Add pburl and pblastreport companion tools to the RPM (#15)

## Why

`node-lookup` output is handy for pivoting to Puppetboard, but there was no quick way to turn a list of hosts into Puppetboard node-page URLs, or to see when each host last ran Puppet. These two small tools close that gap and ship in the **same RPM** so they're available wherever `node-lookup` is.

## Changes

- Add **`pburl`**: reads hostnames from args or piped `node-lookup` output (first field of each line, de-duped) and prints `<host> <puppetboard-node-page-url>`.
- Add **`pblastreport`**: prints `<host>\t<last-report-time>\t<url>` using `report_timestamp` from the PuppetDB v4 `nodes` endpoint. Supports `--relative`/`-r` (relative age) and `--timezone`/`-z <IANA>` (default: local timezone).
- Add **`internal/puppet`** package shared by both tools: config load, PuppetDB `nodes` query, Puppetboard URL construction (`<base>/node/<certname>`), and no-TTY-safe stdin host reading.
- Add **`puppetboard_url`** config key (env `NODE_LOOKUP_PUPPETBOARD_URL`, default `https://puppetboard.k8s.syd1.au.unkin.net`) to the shared config so `config init`/`config show` scaffold it for the whole tool family. `node-lookup`'s own query behaviour is unchanged.
- Build all three binaries individually (each is its own `main` package — a single `go build ./...` can't emit multiple mains) and generate per-binary bash/zsh/fish completions in the Makefile, `build-rpm.sh`, and nfpm spec.
- Cross-compile and attach all three tools per os/arch in the release pipeline; extend `.gitignore`; `go mod tidy` promotes cobra/yaml to direct deps.
- Document the tools, config key, and env var in `AGENTS.md`.

## Testing

- `go test -race ./...` passes (new tests cover config precedence, `nodes` endpoint derivation, host-page URLs, `LookupNode`, stdin host parsing, and the report-time formatting incl. timezone/relative/edge cases).
- Built the RPM locally and confirmed it installs all 3 binaries + 9 completion files.
- Smoke-tested both tools end-to-end against a mock PuppetDB (timezone conversion, relative time, and error handling all correct).

No cross-repo changes needed: the release reuses the existing `default` ServiceAccount and the artifactapi `rpm-internal` upload.

Reviewed-on: #15
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

packaging/nfpm.yaml

@@ -23,13 +23,25 @@ provides:
   - node-lookup
 
 contents:
-  # The CLI binary.
+  # The CLI binaries: node-lookup and its companion tools.
   - src: dist/node-lookup
     dst: /usr/bin/node-lookup
     file_info:
       mode: 0755
       owner: root
       group: root
+  - src: dist/pburl
+    dst: /usr/bin/pburl
+    file_info:
+      mode: 0755
+      owner: root
+      group: root
+  - src: dist/pblastreport
+    dst: /usr/bin/pblastreport
+    file_info:
+      mode: 0755
+      owner: root
+      group: root
 
   # Shell completions (generated by scripts/build-rpm.sh before packaging).
   - src: dist/completions/node-lookup.bash
@@ -44,3 +56,27 @@ contents:
     dst: /usr/share/fish/vendor_completions.d/node-lookup.fish
     file_info:
       mode: 0644
+  - src: dist/completions/pburl.bash
+    dst: /usr/share/bash-completion/completions/pburl
+    file_info:
+      mode: 0644
+  - src: dist/completions/_pburl
+    dst: /usr/share/zsh/site-functions/_pburl
+    file_info:
+      mode: 0644
+  - src: dist/completions/pburl.fish
+    dst: /usr/share/fish/vendor_completions.d/pburl.fish
+    file_info:
+      mode: 0644
+  - src: dist/completions/pblastreport.bash
+    dst: /usr/share/bash-completion/completions/pblastreport
+    file_info:
+      mode: 0644
+  - src: dist/completions/_pblastreport
+    dst: /usr/share/zsh/site-functions/_pblastreport
+    file_info:
+      mode: 0644
+  - src: dist/completions/pblastreport.fish
+    dst: /usr/share/fish/vendor_completions.d/pblastreport.fish
+    file_info:
+      mode: 0644