OSError is too broad — it masks real errors like file-not-found.
ssl.SSLError specifically catches SSL-level disconnects without
swallowing unrelated OSError subtypes.
Closes the test_excludes_broad_oserror CI failure.
- api/helpers.py: _safe_write() now logs disconnects at debug level
instead of silently passing. No more invisible errors.
- server.py: Restructure exception handlers to catch
_CLIENT_DISCONNECT_ERRORS first, then Exception. Remove the
isinstance() filter inside except Exception (LBYL anti-pattern).
The 500-response fallback now catches _CLIENT_DISCONNECT_ERRORS
separately (expected) and logs unexpected failures via
traceback.print_exc() instead of bare except Exception: pass.
- tests/test_broken_pipe_cascade.py: Add coverage for SSL/Timeout
disconnect routing and 500-response safety (both disconnect
survival and unexpected error logging).
