fix: address 5 code review findings (round 8)

- diversity: fix hard_count regression from round 7 — revert to
  'is not None and < 0.85' so only images that actually receive a
  FPS boost (confirmed low confidence) are counted as hard examples;
  None-confidence images use conf_array=1.0 (no boost) and should
  not appear in the hard-example log count
- diversity: fix _scale_bbox_to_thumbnail to use explicit zero-guard
  for imageWidth/imageHeight (meta_w or 0; scale = img_w/meta_w if
  meta_w else 1.0) — mirrors image_processing.py pattern; prevents
  `or img_w` from silently treating imageWidth=0 as missing and
  returning scale=1.0 without surfacing the zero-metadata case
- embeddings: wrap all three os.close calls in _suppress_output
  finally block with try/except OSError: pass so a failed close
  in one branch cannot abort the outer finally and leak devnull_fd
  or the saved_err/saved_out fds
- upload_tracker: clear corrupt flat-list key (data[flat_key] = [])
  after the isinstance warning instead of leaving the corrupt value
  in place — prevents stale IDs persisting across reset_person calls
  and future load_uploaded_ids() from seeing a non-list value
- executor: move 'if pre_fscore is not None: person_has_fscores = True'
  out of the try/except else branch so it fires even when mark_uploaded
  raises; Frigate scores exist once measured regardless of tracker
  write success, and replacement strategy should reflect that

winnow/executor.py

@@ -534,9 +534,8 @@ def upload_to_frigate(jobs: list[dict]) -> None:
                                             " but asset may be re-selected next run: %s",
                                             fname, tracker_exc,
                                         )
-                                    else:
-                                        if pre_fscore is not None:
-                                            person_has_fscores = True
+                                    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