chore: code health review - test fix and error comments (bd-9g1z, bd-ork0)

- Remove TestFindJSONLPathDefault from .test-skip (now passes)
- Add explanatory comments to 24 ignored error locations in cmd/bd:
  - Cobra flag methods (MarkHidden, MarkRequired, MarkDeprecated)
  - Best-effort cleanup/close operations
  - Process signaling operations

Part of code health review epic bd-tggf.

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

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

.test-skip

@@ -1,5 +1,4 @@
 # Tests to skip due to known issues
 # Format: one test name per line (regex patterns supported)
 
-# Issue #356: Expects wrong JSONL filename (issues.jsonl vs beads.jsonl)
-TestFindJSONLPathDefault
+# (no tests currently skipped)