fix(ci): skip claude-mention for bot-authored issues (#1429)

## Summary

- Add `github.event.issue.user.login != 'worktrunk-bot'` to the `issues`
trigger in `claude-mention.yaml`
- Document the new filter in `.github/CLAUDE.md` "Does not trigger" list

## Problem

The hourly review workflow creates issues (like #1424) that incidentally
mention `@worktrunk-bot` in body text — e.g., "comment contained
`@worktrunk-bot`". This triggers `claude-mention` on the `issues` event,
which then duplicates the hourly review's work, including creating a
second fix PR (#1425 vs #1426 for the same issue).

## Fix

Add an author check to skip issues created by `worktrunk-bot` itself,
consistent with the existing `comment.user.login != 'worktrunk-bot'`
loop-prevention checks on `issue_comment` and
`pull_request_review_comment` events.

Closes #1428

## Test plan

- [ ] Verify the `if:` condition syntax is valid (CI should pass)
- [ ] Confirm the next hourly review run doesn't trigger a
claude-mention run on its issues


🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: worktrunk-bot <254187624+worktrunk-bot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: worktrunk-bot

.github/CLAUDE.md

@@ -138,6 +138,7 @@ The mention workflow runs for any user who includes `@worktrunk-bot` — the mer
 - Editing a comment or issue body re-triggers the same response
 
 **Does not trigger:**
+- Issues authored by `worktrunk-bot` (prevents self-triggering when bot-created issues incidentally mention `@worktrunk-bot` in body text)
 - `worktrunk-bot`'s own comments or reviews (loop prevention)
 - Empty approvals on `worktrunk-bot` PRs (approved with no body)
 - Comments on issues or PRs where `worktrunk-bot` hasn't engaged and no `@worktrunk-bot` mention

.github/workflows/claude-mention.yaml

@@ -37,7 +37,8 @@ jobs:
     # for the same reason.)
     if: |
       (github.event_name == 'issues' &&
-        contains(github.event.issue.body, '@worktrunk-bot')) ||
+        contains(github.event.issue.body, '@worktrunk-bot') &&
+        github.event.issue.user.login != 'worktrunk-bot') ||
       (github.event_name == 'issue_comment' &&
         github.event.comment.user.login != 'worktrunk-bot') ||
       (github.event_name == 'pull_request_review_comment' &&