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>

docs/TESTING.md

@@ -67,11 +67,6 @@ Tests in `.test-skip` are automatically skipped. Current broken tests:
    - Issue: Database deadlock, hangs for 5 minutes
    - Impact: Makes test suite extremely slow
 
-2. **TestFindJSONLPathDefault** (GH #356)
-   - Location: `internal/beads/beads_test.go:175`
-   - Issue: Expects `issues.jsonl` but code returns `beads.jsonl`
-   - Impact: Assertion failure
-
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