feat: use top-level key for repo type instead of type field

Replace the flat `remotes:` map (with `type: "remote"/"virtual"/"local"`) with
separate top-level sections — `remote:`, `virtual:`, `local:` — so the repo
type is declared structurally and the `type:` field is no longer needed.

Config loader normalises the new format to the existing internal representation
(injecting `type` into each remote dict), so all handler code is unchanged.
Adds a TestYamlTypeKeys suite covering all three type keys, mixed files, and
field preservation. Includes README migration guide for splitting a single
remotes file into per-type-and-package conf.d files.

examples/conf.d-method/alpine.yaml

@@ -1,7 +1,6 @@
-remotes:
+remote:
   alpine:
     base_url: "https://dl-cdn.alpinelinux.org"
-    type: "remote"
     package: "alpine"
     description: "Alpine Linux APK package repository"
     immutable_patterns:

examples/conf.d-method/github.yaml

@@ -1,7 +1,6 @@
-remotes:
+remote:
   github:
     base_url: "https://github.com"
-    type: "remote"
     package: "generic"
     description: "GitHub releases and files"
     immutable_patterns:

examples/conf.d-method/pypi.yaml

@@ -1,7 +1,6 @@
-remotes:
+remote:
   pypi:
     base_url: "https://files.pythonhosted.org"
-    type: "remote"
     package: "pypi"
     description: "Python Package Index"
     check_mutable_updates: true

examples/single-file/remotes.yaml

@@ -1,5 +1,10 @@
 # Example remotes configuration — copy and adapt for your environment.
 #
+# Top-level keys determine the repository type:
+#   remote:  — proxy to an upstream URL, cache responses in S3
+#   virtual: — merge indexes from multiple member remotes into one
+#   local:   — store files uploaded via PUT, serve via GET
+#
 # immutable_patterns: artifacts cached forever (e.g. release binaries, versioned tags).
 # mutable_patterns:   artifacts that expire after cache.mutable_ttl seconds and are
 #                     re-fetched from upstream on next request (e.g. index files,
@@ -32,10 +37,10 @@
 #database:
 #  url: "postgresql://artifacts:artifacts123@localhost:5432/artifacts"
 #
-remotes:
+
+remote:
   github:
     base_url: "https://github.com"
-    type: "remote"
     package: "generic"
     description: "GitHub releases and files"
     immutable_patterns:
@@ -62,12 +67,11 @@ remotes:
       - "stalwartlabs/stalwart/.*/stalwart-foundationdb-x86_64-unknown-linux-gnu\\.tar\\.gz$"
       - "stalwartlabs/stalwart/.*/stalwart-x86_64-unknown-linux-gnu\\.tar\\.gz$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 0
 
   github-archive:
     base_url: "https://github.com"
-    type: "remote"
     package: "generic"
     description: "GitHub repository archive tarballs"
     immutable_patterns:
@@ -82,23 +86,21 @@ remotes:
     # Only applies to user-defined mutable_patterns, not package-type defaults.
     check_mutable_updates: true
     cache:
-      immutable_ttl: 0       # Tag archives cached indefinitely
-      mutable_ttl: 86400     # Branch archives refreshed after 1 day
+      immutable_ttl: 0      # Tag archives cached indefinitely
+      mutable_ttl: 86400    # Branch archives refreshed after 1 day
 
   gitea-dl:
     base_url: "https://dl.gitea.com"
-    type: "remote"
     package: "generic"
     description: "Gitea download site"
     immutable_patterns:
       - "act_runner/.*/act_runner-.*-linux-amd64$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 0
 
   hashicorp-releases:
     base_url: "https://releases.hashicorp.com"
-    type: "remote"
     package: "generic"
     description: "HashiCorp product releases"
     immutable_patterns:
@@ -114,12 +116,11 @@ remotes:
       - "nomad/.*/nomad_.*_linux_amd64\\.zip$"
       - "packer/.*/packer_.*_linux_amd64\\.zip$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 0
 
   alpine:
     base_url: "https://dl-cdn.alpinelinux.org"
-    type: "remote"
     package: "alpine"
     description: "Alpine Linux APK package repository"
     immutable_patterns:
@@ -128,29 +129,24 @@ remotes:
     # and is always re-fetched on expiry — conditional checks are skipped for
     # built-in mutable patterns regardless of this flag.
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 7200  # Index files (APKINDEX.tar.gz) cached for 2 hours
 
   almalinux:
     base_url: "https://gsl-syd.mm.fcix.net/almalinux"
-    type: "remote"
     package: "rpm"
     description: "AlmaLinux RPM package repository"
     immutable_patterns:
       - ".*/x86_64/.*\\.rpm$"
       - ".*/noarch/.*\\.rpm$"
       - ".*/repodata/.*$"
-      - ".*\\.rpm$"  # Allow all RPM files
-    # repomd.xml / repodata are package-type defaults — always re-fetched on
-    # expiry. check_mutable_updates would only apply to any custom
-    # mutable_patterns added here.
+      - ".*\\.rpm$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 7200  # Metadata files cached for 2 hours
 
   epel:
     base_url: "http://mirror.aarnet.edu.au/pub/epel"
-    type: "remote"
     package: "rpm"
     description: "EPEL (Extra Packages for Enterprise Linux)"
     immutable_patterns:
@@ -160,12 +156,11 @@ remotes:
       - ".*/noarch/.*\\.rpm$"
       - ".*/repodata/.*$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
-      mutable_ttl: 7200  # Metadata files cached for 2 hours
+      immutable_ttl: 0
+      mutable_ttl: 7200
 
   fedora:
     base_url: "https://gsl-syd.mm.fcix.net/fedora/linux"
-    type: "remote"
     package: "rpm"
     description: "Fedora Linux RPM package repository"
     immutable_patterns:
@@ -175,26 +170,21 @@ remotes:
       - ".*/noarch/.*\\.rpm$"
       - "updates/.*/Everything/x86_64/repodata/.*$"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 300  # Metadata files cached for 5 minutes
 
   ghcr:
     base_url: "https://ghcr.io"
-    type: "remote"
     package: "docker"
     description: "GitHub Container Registry"
     # username: "your-github-username"
     # password: "your-github-pat"  # needs read:packages scope
-    # Docker manifest/tag-list patterns are package-type defaults — always
-    # re-fetched on expiry. check_mutable_updates only applies to any custom
-    # mutable_patterns you add (e.g. a metadata endpoint).
     cache:
       immutable_ttl: 0
       mutable_ttl: 300
 
   dockerhub:
     base_url: "https://registry-1.docker.io"
-    type: "remote"
     package: "docker"
     description: "Docker Hub registry"
     cache:
@@ -203,15 +193,9 @@ remotes:
 
   pypi:
     base_url: "https://files.pythonhosted.org"
-    type: "remote"
     package: "pypi"
     description: "Python Package Index — simple index and package files via a single remote"
-    # simple/ requests are transparently fetched from pypi.org; package files come from
-    # files.pythonhosted.org (base_url). URLs in the simple index are rewritten to this remote.
     check_mutable_updates: true
-    # Block packages published within the last 3 days (supply-chain attack mitigation).
-    # Immutable artifacts (wheel/sdist) newer than quarantine_days return 404 until
-    # the window passes. Disable by setting quarantine_new: false or removing both keys.
     quarantine_new: true
     quarantine_days: 3
     immutable_patterns:
@@ -226,7 +210,6 @@ remotes:
 
   pypi-gitea:
     base_url: "https://gitea.example.com/api/packages/myorg/pypi"
-    type: "remote"
     package: "pypi"
     description: "Private Gitea PyPI registry — simple index and files at the same host"
     # username: "your-gitea-username"
@@ -244,7 +227,6 @@ remotes:
 
   npm:
     base_url: "https://registry.npmjs.org"
-    type: "remote"
     package: "npm"
     description: "npm registry — package metadata with tarball URL rewriting"
     check_mutable_updates: true
@@ -258,19 +240,17 @@ remotes:
 
   hashicorp-helm:
     base_url: "https://helm.releases.hashicorp.com"
-    type: "remote"
     package: "helm"
     description: "HashiCorp Helm chart repository (Vault, Consul, Nomad, etc.)"
     check_mutable_updates: true
     immutable_patterns:
       - "\\.tgz$"
     cache:
-      immutable_ttl: 0    # Chart tarballs are versioned — cache forever
-      mutable_ttl: 3600   # index.yaml refreshed after 1 hour
+      immutable_ttl: 0
+      mutable_ttl: 3600
 
   metallb:
     base_url: "https://metallb.github.io/metallb"
-    type: "remote"
     package: "helm"
     description: "MetalLB load balancer Helm charts"
     check_mutable_updates: true
@@ -282,7 +262,6 @@ remotes:
 
   jetstack:
     base_url: "https://charts.jetstack.io"
-    type: "remote"
     package: "helm"
     description: "Jetstack Helm charts (cert-manager)"
     check_mutable_updates: true
@@ -294,7 +273,6 @@ remotes:
 
   rancher-stable:
     base_url: "https://releases.rancher.com/server-charts/stable"
-    type: "remote"
     package: "helm"
     description: "Rancher stable Helm charts"
     check_mutable_updates: true
@@ -306,7 +284,6 @@ remotes:
 
   purelb:
     base_url: "https://gitlab.com/api/v4/projects/20400619/packages/helm/stable"
-    type: "remote"
     package: "helm"
     description: "PureLB load balancer Helm charts"
     check_mutable_updates: true
@@ -318,7 +295,6 @@ remotes:
 
   istio:
     base_url: "https://istio-release.storage.googleapis.com/charts"
-    type: "remote"
     package: "helm"
     description: "Istio service mesh Helm charts"
     check_mutable_updates: true
@@ -330,7 +306,6 @@ remotes:
 
   cnpg:
     base_url: "https://cloudnative-pg.github.io/charts"
-    type: "remote"
     package: "helm"
     description: "CloudNativePG operator Helm charts"
     check_mutable_updates: true
@@ -342,7 +317,6 @@ remotes:
 
   ceph-csi:
     base_url: "https://ceph.github.io/csi-charts"
-    type: "remote"
     package: "helm"
     description: "Ceph CSI driver Helm charts"
     check_mutable_updates: true
@@ -354,7 +328,6 @@ remotes:
 
   external-dns:
     base_url: "https://kubernetes-sigs.github.io/external-dns/"
-    type: "remote"
     package: "helm"
     description: "ExternalDNS Helm charts"
     check_mutable_updates: true
@@ -366,7 +339,6 @@ remotes:
 
   intel-helm:
     base_url: "https://intel.github.io/helm-charts/"
-    type: "remote"
     package: "helm"
     description: "Intel Helm charts"
     check_mutable_updates: true
@@ -378,7 +350,6 @@ remotes:
 
   elastic:
     base_url: "https://helm.elastic.co"
-    type: "remote"
     package: "helm"
     description: "Elastic stack Helm charts"
     check_mutable_updates: true
@@ -390,7 +361,6 @@ remotes:
 
   k8up-io:
     base_url: "https://k8up-io.github.io/k8up"
-    type: "remote"
     package: "helm"
     description: "K8up backup operator Helm charts"
     check_mutable_updates: true
@@ -402,7 +372,6 @@ remotes:
 
   victoriametrics:
     base_url: "https://victoriametrics.github.io/helm-charts/"
-    type: "remote"
     package: "helm"
     description: "VictoriaMetrics observability Helm charts"
     check_mutable_updates: true
@@ -414,7 +383,6 @@ remotes:
 
   grafana:
     base_url: "https://grafana.github.io/helm-charts"
-    type: "remote"
     package: "helm"
     description: "Grafana observability Helm charts"
     check_mutable_updates: true
@@ -426,7 +394,6 @@ remotes:
 
   helm-openldap:
     base_url: "https://jp-gouin.github.io/helm-openldap/"
-    type: "remote"
     package: "helm"
     description: "OpenLDAP Helm charts"
     check_mutable_updates: true
@@ -438,7 +405,6 @@ remotes:
 
   woodpecker:
     base_url: "https://woodpecker-ci.org/"
-    type: "remote"
     package: "helm"
     description: "Woodpecker CI Helm charts"
     check_mutable_updates: true
@@ -450,7 +416,6 @@ remotes:
 
   stakater:
     base_url: "https://stakater.github.io/stakater-charts"
-    type: "remote"
     package: "helm"
     description: "Stakater Helm charts"
     check_mutable_updates: true
@@ -462,7 +427,6 @@ remotes:
 
   jfrog:
     base_url: "https://charts.jfrog.io/"
-    type: "remote"
     package: "helm"
     description: "JFrog Helm charts"
     check_mutable_updates: true
@@ -474,7 +438,6 @@ remotes:
 
   openvox:
     base_url: "https://openvoxproject.github.io/openvox-helm-chart"
-    type: "remote"
     package: "helm"
     description: "OpenVox Helm charts"
     check_mutable_updates: true
@@ -484,8 +447,8 @@ remotes:
       immutable_ttl: 0
       mutable_ttl: 3600
 
+virtual:
   helm-all:
-    type: "virtual"
     package: "helm"
     description: "Virtual repository merging all helm remotes — member order is priority order for duplicate chart+version"
     members:
@@ -509,10 +472,10 @@ remotes:
       - jfrog
       - openvox
 
+local:
   local-generic:
-    type: "local"
     package: "generic"
     description: "Local generic file repository"
     cache:
-      immutable_ttl: 0  # Files cached indefinitely
+      immutable_ttl: 0
       mutable_ttl: 0