Publish vendor RPMs to artifactapi rpm-vendor, one package per job

Builds currently push to Gitea's RPM registry and run build-all in a single
job. Publish instead to the artifactapi rpm-vendor local repos (real yum
repos; repodata regenerates automatically) and give each vendor package its
own job so failures are isolated and builds parallelise. Because builds no
longer land in Gitea, the "skip already-built version" check now probes
artifactapi.

- tools/build: repoint check_package_exists from the Gitea packages API to
  the artifactapi rpm-vendor repo (GET the served Packages/<file>.rpm path).
  Add get_vendor_repo() (distro -> rpm-vendor-<suffix>) and get_rpm_arch()
  (amd64 -> x86_64), and carry arch on PackageInfo so the probed filename
  matches the built RPM.
- .woodpecker: replace the per-distro build-all pipelines with per-distro
  matrix pipelines over PACKAGE, so each package builds in its own job.
  deploy-*.yaml (master push) build each package and PUT its RPM to the
  distro's rpm-vendor repo; build-*.yaml (pull_request) build as a check.
- tools/gen-pipelines + `make pipelines`: generate the .woodpecker matrix
  pipelines from rpms/*/metadata.yaml (source of truth for target distros);
  regenerate after adding or removing packages.

tools/gen-pipelines

@@ -0,0 +1,147 @@
+#!/usr/bin/env -S uv run --script
+# /// script
+# dependencies = [
+#   "pyyaml",
+# ]
+# ///
+
+# vim: filetype=python
+
+"""
+Generate Woodpecker pipelines for rpmbuilder.
+
+One pipeline file per distro (build-<distro>.yaml for pull_request checks and
+deploy-<distro>.yaml for master pushes). Each pipeline uses a Woodpecker matrix
+over the packages that target that distro, so every vendor package builds in its
+own job. Deploy jobs publish to the distro's artifactapi rpm-vendor local repo.
+
+The matrix package lists are derived from each rpms/*/metadata.yaml, so this
+script is the source of truth: run `make pipelines` (or ./tools/gen-pipelines)
+after adding/removing a package or changing its target distros, and commit the
+regenerated .woodpecker/*.yaml.
+"""
+
+import glob
+from pathlib import Path
+
+import yaml
+
+ROOT = Path(__file__).resolve().parent.parent
+WOODPECKER = ROOT / ".woodpecker"
+
+# Distro -> pipeline settings. `builder` runs buildah/the build tool (the actual
+# RPM build happens in a nested container using each package's metadata image);
+# `upload` only needs curl. rpm-vendor-<suffix> mirrors the artifactapi repos.
+DISTROS = [
+    {"key": "almalinux8", "distro": "almalinux/el8", "repo": "rpm-vendor-el8"},
+    {"key": "almalinux9", "distro": "almalinux/el9", "repo": "rpm-vendor-el9"},
+    {"key": "fedora42", "distro": "fedora/42", "repo": "rpm-vendor-f42"},
+    {"key": "fedora43", "distro": "fedora/43", "repo": "rpm-vendor-f43"},
+    {"key": "fedora44", "distro": "fedora/44", "repo": "rpm-vendor-f44"},
+]
+
+BUILDER_IMAGE = "git.unkin.net/unkin/almalinux9-rpmbuilder:latest"
+UPLOAD_IMAGE = "git.unkin.net/unkin/almalinux9-base:latest"
+ARTIFACTAPI = "https://artifactapi.k8s.syd1.au.unkin.net"
+
+HEADER = "# Generated by tools/gen-pipelines - do not edit by hand.\n"
+
+
+def packages_for(distro: str) -> list[str]:
+    names = []
+    for mf in sorted(glob.glob(str(ROOT / "rpms" / "*" / "metadata.yaml"))):
+        meta = yaml.safe_load(open(mf)) or {}
+        distros = {
+            repo
+            for build in meta.get("builds", [])
+            for repo in build.get("repository", [])
+        }
+        if distro in distros:
+            names.append(meta.get("name", Path(mf).parent.name))
+    return sorted(names)
+
+
+def matrix_block(packages: list[str]) -> str:
+    lines = "\n".join(f"    - {p}" for p in packages)
+    return f"matrix:\n  PACKAGE:\n{lines}\n"
+
+
+def build_step() -> str:
+    return f"""  - name: build
+    image: {BUILDER_IMAGE}
+    commands:
+      - mkdir -p /woodpecker/rpms
+      - ln -s /woodpecker/rpms /workspace
+      - ./tools/build build --distro DISTRO --buildah "$PACKAGE"
+    privileged: true
+    backend_options:
+      kubernetes:
+        serviceAccountName: default
+        resources:
+          requests:
+            memory: 512Mi
+            cpu: 1
+          limits:
+            memory: 2Gi
+            cpu: 2
+"""
+
+
+def upload_step(repo: str) -> str:
+    return f"""  - name: upload
+    image: {UPLOAD_IMAGE}
+    commands:
+      - |
+        HOST="{ARTIFACTAPI}"
+        REPO="{repo}"
+        for rpm in $(find dist -type f -name '*.rpm'); do
+          FILE=$$(basename "$$rpm")
+          # artifactapi has no HEAD route (405); probe the served Packages path.
+          code=$$(curl -s -o /dev/null -w '%{{http_code}}' "$$HOST/api/v2/remotes/$$REPO/files/Packages/$$FILE" || true)
+          if [ "$$code" = "200" ]; then
+            echo "$$FILE already exists in $$REPO (HTTP $$code); skipping upload"
+            continue
+          fi
+          echo "Uploading $$FILE to $$REPO (existence probe returned $$code)"
+          curl -f -X PUT \\
+            "$$HOST/api/v2/remotes/$$REPO/files/$$FILE" \\
+            -H "Content-Type: application/x-rpm" \\
+            --data-binary @"$$rpm"
+        done
+    depends_on: [build]
+    backend_options:
+      kubernetes:
+        serviceAccountName: default
+        resources:
+          requests:
+            memory: 128Mi
+            cpu: 100m
+          limits:
+            memory: 512Mi
+            cpu: 500m
+"""
+
+
+def render(distro_cfg: dict, deploy: bool) -> str:
+    packages = packages_for(distro_cfg["distro"])
+    if deploy:
+        when = "when:\n  - event: push\n    branch: master\n"
+    else:
+        when = "when:\n  - event: pull_request\n"
+    body = HEADER + when + "\n" + matrix_block(packages) + "\nsteps:\n"
+    body += build_step().replace("DISTRO", distro_cfg["distro"])
+    if deploy:
+        body += "\n" + upload_step(distro_cfg["repo"])
+    return body
+
+
+def main() -> None:
+    for cfg in DISTROS:
+        (WOODPECKER / f"build-{cfg['key']}.yaml").write_text(render(cfg, deploy=False))
+        (WOODPECKER / f"deploy-{cfg['key']}.yaml").write_text(render(cfg, deploy=True))
+        print(f"generated build-{cfg['key']}.yaml deploy-{cfg['key']}.yaml "
+              f"({len(packages_for(cfg['distro']))} packages)")
+
+
+if __name__ == "__main__":
+    main()