Tighten cleanup criterion and record branch-naming…

Details

Two related fixes:
1. Cleanup workflow: previously deleted every branch with no open PR. That
   would also catch brand-new branches nobody had opened a PR on yet (i.e.
   in-progress work). Tighten the criterion to require BOTH a CLOSED PR AND
   no OPEN PR — concluded work only. A no-PR branch is reported as skipped
   rather than deleted. Also document recovery via refs/pull/<N>/head in the
   workflow header.
2. CLAUDE.md: fold in the meaningful-branch-name rule from commit 92b8605
   (which was added on the still-open PR #18 branch claude/exciting-allen-joes9n
   and never merged to main, so it was effectively lost when this session's
   CLAUDE.md replaced the orphan). Branches must use type/short-description
   (chore/, fix/, feat/) — no claude/<auto-generated> placeholders. Also
   document branch-cleanup hygiene (this workflow and the auto-delete repo
   setting).
This branch's own name (chore/cleanup-criterion-and-naming-rule) follows
the rule it adds.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pn8V4h9YWbjYzdSrDiLiVL

Files changed (2)