docs: closed-not-merged PR reconciliation rules (#51)

Documents and enforces rules for closed-not-merged PR reconciliation, direct-master-push prevention, and issue label cleanup.

Rules added:
- Explicit definitions for Merged, Landed, Closed-not-merged, and Reconciled.
- A PR is done only when Gitea reports it merged or reconciliation proves content is present on master.
- Direct push to master is forbidden except as a documented recovery exception.
- PRs closed but not merged trigger the reconciliation process.
- Branch and worktree cleanup is forbidden until merge or reconciliation is confirmed.
- Final reports require PR metadata and Git content verification.

Closes #51.

skills/llm-project-workflow/templates/merge-pr.md

@@ -10,6 +10,7 @@ Rules (llm-project-workflow):
   author → STOP.
 - Do not merge unless the PR is open, mergeable, and its checks/review pass.
 - No force-merge, no bypassing branch protections.
+- If the PR is closed but `merged=false`, STOP and run reconciliation. Do not clean up.
 
 Steps:
 1. Verify authenticated identity + active profile.
@@ -20,9 +21,9 @@ Steps:
 5. Confirm remote master now contains the merge commit.
 
 Then run the cleanup template (worktree-cleanup.md):
-- close/release issue #<n>, remove status:in-progress
+- close/release issue #<n>, remove status:in-progress (if it cannot be removed, report why)
 - delete remote branch, remove local branch + worktree folder
 - fetch/prune; confirm main checkout is clean and current (0 0).
 
-Handoff: reviewer identity, merge result + commit, cleanup done, issue closed.
+Handoff: reviewer identity, merge result + commit, cleanup done, issue closed, PR metadata state/merged flag/hash, remote master hash & Git content check.
 ```