Add agentpr and watchpr CLI tools

agentpr manages PRs/comments/whoami as unkin-agent (Vault AppRole -> gitea creds
-> Gitea API), fixing tea's post-as-Ben default. watchpr polls PRs and alerts
only on merge/close, human comment, CI failure, or lost mergeability.

- cobra multi-binary layout mirroring node-lookup (cmd/ + internal/)
- Makefile (build, patch|minor|major, completions, rpm), nfpm RPM with both
  binaries + bash/zsh/fish completions, woodpecker CI publishing to rpm-internal
- unit tests for parsing, meaningful-change detection, and the Vault+Gitea client

.gitignore

@@ -0,0 +1,7 @@
+# built binaries (repo root only — not the cmd/ source dirs)
+/agentpr
+/watchpr
+# cross-compiled release artifacts (e.g. agentpr-linux-amd64)
+/agentpr-*
+/watchpr-*
+dist/