docs: add portable llm-project-workflow skill + templates (#46)

Extract the project's operating rules into a reusable, project-agnostic skill
so any repo can adopt the same safe LLM workflow.

- skills/llm-project-workflow/SKILL.md: issue-first; isolated branch worktrees
  (main checkout = orchestration only); distinct author/reviewer identities and
  profile safety (secrets by reference only; stop if authenticated user == PR
  author); branch naming; start/review/merge/cleanup workflows; fail-closed
  cases; recovery patterns; and an "Adapting to a project" table for the
  forge-specific names.
- templates/: copy/paste prompts for start-issue, review-pr, merge-pr,
  recover-bad-state, worktree-cleanup.
- Link the skill from README.md and docs/llm-workflow-runbooks.md (the runbook
  is framed as the Gitea-specific application of the portable skill).

Docs-only; no code, no secrets, safe placeholder examples only. No change to
MCP runtime, Gitea API, credential storage, or worktree helpers.

Checks: full suite 287 passed / 0 failures; git diff --check clean; secret scan
of skills/ clean.

Closes #46. Refs #38, #39.

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

skills/llm-project-workflow/templates/recover-bad-state.md

@@ -0,0 +1,32 @@
+# Template: recover from bad state
+
+Copy, fill the `<...>` fields, paste as the task prompt. Recovery is read-then-
+act: gather facts first, never discard unmerged work.
+
+```text
+Task: recover repo state for <situation>. Do not lose unmerged work.
+
+Rules (llm-project-workflow):
+- Fail closed: if state is unclear or a step would delete unmerged work, STOP.
+- Never push master. Never discard commits not safely pushed to <remote>.
+
+Diagnose first:
+1. git fetch <remote> --prune
+2. git status --short; git worktree list
+3. git rev-list --left-right --count <remote>/master...master   # ahead/behind
+4. For any PR involved: confirm state (open/closed/merged) AND whether
+   <remote>/master actually contains its commits ("closed" != "merged").
+
+Act per case:
+- Dirty worktree from another issue: leave it; start yours in a new worktree.
+- Local master ahead of remote: confirm the extra commits live on a branch
+  pushed to <remote>, THEN git reset --hard <remote>/master. Verify with
+  `git branch --contains <sha>` first.
+- PR closed but not merged: re-push the branch, reopen/replace the PR, let an
+  eligible reviewer merge. Do not merge your own.
+- Branch deleted before merge: recover commits from a local branch/reflog (or
+  git fsck --lost-found), re-push, reopen the PR.
+- Unauthorized untracked file: do not commit it; leave pre-existing artifacts.
+
+Handoff: what was wrong, evidence, action taken, current state, what remains.
+```