fix: address 2 code review findings (round 9)

- executor: revert person_has_fscores=True back into try/except else
  branch; moving it outside in round 8 was a regression — when the
  tracker write fails on the first-ever upload (no prior frigate_scores
  in tracker), setting the flag True prematurely switches at-cap
  replacement into fscore mode, get_most_redundant_mapped_file returns
  None (no entries), and all replacements are silently skipped;
  the flag must only be set when the score is actually written
- diversity: remove dead face_crop-None guard; any face that passes
  assess_quality (≥90 px MIN_FACE_WIDTH) produces a crop ≥135 px
  (face + 25% margin), which is always above the 30 px crop minimum,
  making the guard unreachable; _crop_face_from_thumbnail also calls
  _get_face_bbox internally, so face_bbox is not None guarantees the
  inner bbox check also passes

winnow/executor.py

@@ -534,8 +534,9 @@ def upload_to_frigate(jobs: list[dict]) -> None:
                                             " but asset may be re-selected next run: %s",
                                             fname, tracker_exc,
                                         )
-                                    if pre_fscore is not None:
-                                        person_has_fscores = True
+                                    else:
+                                        if pre_fscore is not None:
+                                            person_has_fscores = True
                                     # Always record for reconcile so the Frigate filename→asset_id
                                     # mapping is created even when the tracker write fails.
                                     # Trade-off: if mark_uploaded failed, asset_id is absent from