docs: add LLM-operated Gitea workflow runbooks (#17)

Add docs/llm-workflow-runbooks.md — the final roadmap #10 deliverable:
operational runbooks for LLM-operated Gitea workflows, built on the shipped
canonical profiles + interactive menu + gated review/merge + audit logging.

Covers:
- Principle: the profile is the role, not the LLM (task-scoped, not assigned).
- Canonical config: GITEA_MCP_CONFIG / GITEA_MCP_PROFILE, version, profiles,
  keychain + env auth references, precedence, legacy env-only fallback.
- Interactive menu (python gitea_config.py menu): create author/reviewer
  profiles, generate Claude/Gemini/Codex launcher snippets, validate auth,
  check PR reviewer eligibility.
- Thin-launcher pattern: LLM configs carry only command/args + the two
  GITEA_MCP_* vars — never raw tokens/passwords.
- Migration away from duplicated GITEA_USER_*/GITEA_PASS_*/GITEA_SITE_* blocks;
  secrets referenced by keychain id or env var name only.
- Per-workflow runbooks (create issue/children, implement+PR, review/request-
  changes/approve, merge, close-after-merge, stop-on-blocker) with safe prompts.
- Fail-closed behavior table (unknown identity/profile, self-author, moved head,
  unexpected files, detected secrets, production/deploy) and no self-review/merge.

Docs-only: no implementation code. Safe placeholder examples only (no real
tokens, passwords, usernames, or private config). README links the new runbook.

Closes #17. Refs #10.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -182,7 +182,10 @@ Notes:
   `gitea_get_profile` returns the full non-secret profile metadata so a workflow
   can inspect which runtime it is talking to before deciding to act.
 - See [`docs/gitea-execution-profiles.md`](docs/gitea-execution-profiles.md) for
-  the full profile model.
+  the full profile model, and
+  [`docs/llm-workflow-runbooks.md`](docs/llm-workflow-runbooks.md) for the
+  task-scoped, profile-based runbooks (create/review/merge/close, thin
+  launchers, migration, fail-closed rules).
 - **Audit logging (#18):** mutating actions emit a durable, redacted JSON audit
   record — timestamp, action, result (`allowed`/`blocked`/`failed`/`succeeded`),
   profile name + audit label, authenticated username, target repo/issue/PR,