fix(doctor): remove circular error message in --fix mode

When `bd doctor --fix` fails to apply a fix, it was showing
"Manual fix: Run 'bd doctor --fix' ..." which is circular and unhelpful.

Now extracts just the manual command from the fix message:
- "..., or manually: <cmd>" -> extracts <cmd>
- "bd doctor --fix or <alt>" -> extracts <alt>
- No alternative available -> shows nothing

Closes GH#403

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.beads/.gitignore

@@ -30,3 +30,5 @@ beads.right.meta.json
 !issues.jsonl
 !metadata.json
 !config.json
+deletions.jsonl
+deletions.jsonl.migrated