feat(suggestions): tag-input dropdown searches the full prediction set

The typed dropdown sourced the threshold-filtered panel list (>= 0.70 general),
so low-confidence actions/features the model DID predict never appeared — forcing
hand-typed custom tags instead of accepting the model's canonical formatting.

Add a threshold override: SuggestionService.for_image(threshold_override=) and
GET /images/<id>/suggestions?min=<f> surface EVERY stored prediction (down to the
0.05 store floor), alias-resolved and normalized, still excluding applied/rejected
and unsurfaced categories. The suggestions store gains allByCategory + loadAll
(min=0); the dropdown searches that full set (cap 20), while the Suggestions panel
stays curated at the configured threshold. Accept/dismiss drop from both lists.

Operator-asked 2026-06-09. Test: a 0.30 general prediction is hidden by default
but surfaced with threshold_override=0.0; unsurfaced categories still excluded.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_ml_suggestions.py

@@ -44,6 +44,33 @@ async def test_threshold_filters_low_confidence_general(db):
     assert "Lowconf" not in names
 
 
+@pytest.mark.asyncio
+async def test_threshold_override_surfaces_low_confidence(db):
+    # The typed-dropdown "show everything the model saw" mode: threshold_override
+    # surfaces stored predictions below the configured threshold (in canonical
+    # formatting) so they can be picked instead of hand-typed (2026-06-09).
+    img = _img(
+        "d" * 64,
+        {
+            "lowconf": {"category": "general", "confidence": 0.30},
+            "sword": {"category": "general", "confidence": 0.97},
+        },
+    )
+    db.add(img)
+    await db.flush()
+    sl = await SuggestionService(db).for_image(img.id, threshold_override=0.0)
+    names = [s.display_name for s in sl.by_category.get("general", [])]
+    assert "Sword" in names
+    assert "Lowconf" in names  # below the configured threshold, surfaced anyway
+
+    # Unsurfaced categories are still excluded even with the override.
+    img2 = _img("e" * 64, {"safe": {"category": "rating", "confidence": 0.99}})
+    db.add(img2)
+    await db.flush()
+    sl2 = await SuggestionService(db).for_image(img2.id, threshold_override=0.0)
+    assert "rating" not in sl2.by_category
+
+
 @pytest.mark.asyncio
 async def test_unsurfaced_category_dropped(db):
     img = _img(