Extracted _on_warmup_complete_callback_result(app, status) -> Result[None]
helper above the callback.
ANTI-SLIMING: full Result[T] propagation (NO except+pass-after-log). The
helper returns Result(data=None) on success or Result(data=None,
errors=[ErrorInfo]) on exception (logging NOT a drain per the user's
principle 2026-06-17).
The legacy _on_warmup_complete_callback preserves its signature, calls
the helper, and drains to app.controller._worker_errors with the
controller lock acquired on append (thread-safety critical per
sub-track 4 spec).
Tests: 2 new tests verify both paths (success and RuntimeError).
Audit: L4911 reclassified from INTERNAL_SILENT_SWALLOW (4 sites remaining,
was 5). New helper L4911 is INTERNAL_COMPLIANT.