Address review feedback from @nesquena-hermes on PR #3210:
1. Deduplicate _CLIENT_DISCONNECT_ERRORS:
- Single authoritative definition in api/helpers.py
- api/routes.py now imports from api.helpers instead of defining
its own copy with different membership
- Unified tuple uses OSError (covers ssl.SSLError since it
subclasses OSError) — broad socket-level disconnect coverage
2. Remove github-search-report.md:
- Research scratch output that doesn't belong in the repo root
- Content belongs in PR description or a gist
3. Docstring improvement:
- Added comment explaining why OSError covers ssl.SSLError
- Documents the errno-level socket errors caught by OSError