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

internal/agent/parse.go

@@ -0,0 +1,59 @@
+package agent
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// PRRef identifies a single pull request by repository and number.
+type PRRef struct {
+	Owner  string
+	Repo   string
+	Number int
+}
+
+// String renders the ref in canonical owner/repo#N form.
+func (r PRRef) String() string {
+	return fmt.Sprintf("%s/%s#%d", r.Owner, r.Repo, r.Number)
+}
+
+// RepoPath returns the "owner/repo" portion used in Gitea API URLs.
+func (r PRRef) RepoPath() string {
+	return r.Owner + "/" + r.Repo
+}
+
+// ParsePRRef parses "owner/repo#N" or "owner/repo:N" into a PRRef.
+func ParsePRRef(s string) (PRRef, error) {
+	s = strings.TrimSpace(s)
+	sep := strings.IndexAny(s, "#:")
+	if sep < 0 {
+		return PRRef{}, fmt.Errorf("invalid PR reference %q: expected owner/repo#N or owner/repo:N", s)
+	}
+	repoPart := s[:sep]
+	numPart := s[sep+1:]
+
+	owner, repo, ok := strings.Cut(repoPart, "/")
+	if !ok || owner == "" || repo == "" {
+		return PRRef{}, fmt.Errorf("invalid PR reference %q: repo must be owner/repo", s)
+	}
+	if strings.Contains(repo, "/") {
+		return PRRef{}, fmt.Errorf("invalid PR reference %q: repo must be owner/repo", s)
+	}
+
+	n, err := strconv.Atoi(numPart)
+	if err != nil || n <= 0 {
+		return PRRef{}, fmt.Errorf("invalid PR reference %q: PR number must be a positive integer", s)
+	}
+	return PRRef{Owner: owner, Repo: repo, Number: n}, nil
+}
+
+// ParseRepo validates and splits an "owner/repo" string.
+func ParseRepo(s string) (owner, repo string, err error) {
+	s = strings.TrimSpace(s)
+	owner, repo, ok := strings.Cut(s, "/")
+	if !ok || owner == "" || repo == "" || strings.Contains(repo, "/") {
+		return "", "", fmt.Errorf("invalid repo %q: expected owner/repo", s)
+	}
+	return owner, repo, nil
+}