refactor(tags): unify suggestion source — one canonical DB-tag dropdown, drop dead raw/alias machinery (#154)

Every tag suggestion is a canonical DB tag now (tagging-v2 #114: heads + CCIP
score EXISTING concept tags). The pre-heads apparatus for model-predicted tags
that didn't exist in the DB — creates_new_tag / raw_name / via_alias, the
/suggestions/alias endpoint + add_alias_and_accept, AliasPickerDialog, and the
store's aliasAccept/removeAlias — was dead and is removed.

The type-to-add dropdown was TWO row sources (server autocomplete + the image's
ML suggestions) merged with a dedup that dropped the %-bearing suggestion row
when the debounced server hit landed — the operator's "confidence % flickers
then vanishes". Now it's ONE list of DB-tag matches, each annotated with the
model's confidence (join by canonical_tag_id) when the tag was scored for this
image. No dedup, no flicker; picking a suggested tag still records acceptance
via TagPanel.findPending.

Single per-image fetch: score_image now reports above_threshold per row
(computed vs the head's own suggest cut, separate from the inclusion floor), so
the rail makes ONE min=0 request and derives the panel (above_threshold) and the
dropdown (all, text-filtered) client-side — the two /suggestions calls collapse
to one. Manual "Create 'X' as <kind>" (novel typed names) is unchanged; the
alias table + tag-side alias admin + auto-apply alias matching are untouched.

Tests: gate/serializer assertions updated (above_threshold; dropped dead-field
+ alias-endpoint checks); frontend spec seeds via the single load and covers the
byCategory/aboveByCategory split.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CgZP9v2otxVJymiYsnVuMy

backend/app/services/ml/suggestions.py

@@ -22,22 +22,20 @@ from .heads import score_image
 
 @dataclass(frozen=True)
 class Suggestion:
-    # canonical_tag_id is None when this is a raw Camie tag with no alias and
-    # no existing Tag row — accepting it will create the tag.
-    canonical_tag_id: int | None
+    # Every suggestion is a canonical Tag: heads/CCIP only score EXISTING concept
+    # tags (tagging-v2, #114). The old raw-model-key / creates-new / alias-remap
+    # cases are gone — a suggestion always maps to a real tag id.
+    canonical_tag_id: int
     display_name: str
     category: str
     score: float
     source: str  # 'head' | 'ccip' | 'both' (Camie tagger/centroid removed in v2)
-    creates_new_tag: bool
-    # raw_name = the booru model vocab key behind this suggestion. It's the key
-    # an alias MUST be stored under (resolution looks up the raw key), so the
-    # modal needs it to author an alias correctly. None for centroid-only hits
-    # (no underlying prediction → nothing to alias).
-    raw_name: str | None = None
-    # via_alias = this suggestion was surfaced because an operator alias remapped
-    # the raw prediction to this canonical tag. Lets the UI mark it + offer undo.
-    via_alias: bool = False
+    # above_threshold = the score cleared the head's own suggest cut (or the
+    # system floor). The Suggestions PANEL shows only these; the typed-tag
+    # dropdown fetches ALL suggestions (every head, min=0) and just annotates each
+    # matching row with its score, so a low-confidence concept can still be typed
+    # and picked. CCIP character matches are always above their match threshold.
+    above_threshold: bool
     # rejected = the operator dismissed this tag for this image (a stored
     # TagSuggestionRejection). It stays in the list — flagged, not dropped — so
     # the rejection is VISIBLE and REVERSIBLE in the rail (misclick recovery,
@@ -108,6 +106,7 @@ class SuggestionService:
         for h in hits:
             merged[(h["category"], h["tag_id"])] = {
                 "name": h["name"], "score": h["score"], "source": "head",
+                "above_threshold": h["above_threshold"],
                 "grounding": h.get("grounding"),
             }
         for c in ccip_hits:
@@ -116,12 +115,16 @@ class SuggestionService:
             if ex is not None:
                 ex["source"] = "both"
                 ex["score"] = max(ex["score"], c["score"])
+                # CCIP only returns matches above its own threshold, so a CCIP
+                # corroboration always makes the merged suggestion above-threshold.
+                ex["above_threshold"] = True
                 # Keep the head's localized crop if it had one; else fall back to
                 # the CCIP figure so a corroborated character still grounds (#1206).
                 ex["grounding"] = ex.get("grounding") or c.get("grounding")
             else:
                 merged[key] = {
                     "name": c["name"], "score": c["score"], "source": "ccip",
+                    "above_threshold": True,
                     "grounding": c.get("grounding"),
                 }
 
@@ -136,7 +139,7 @@ class SuggestionService:
                     category=cat,
                     score=m["score"],
                     source=m["source"],
-                    creates_new_tag=False,
+                    above_threshold=m["above_threshold"],
                     rejected=tag_id in rejected,
                     grounding=m.get("grounding"),
                 )
@@ -157,8 +160,7 @@ class SuggestionService:
         was suggested for (or already applied to) >= threshold fraction of
         the selection AND was acceptable on >= 1 image. Confidence is the
         mean over images where it was suggested. Aggregated by
-        canonical_tag_id; creates-new (no canonical id) suggestions are
-        skipped (bulk Accept applies by tag id)."""
+        canonical_tag_id (every suggestion is a canonical tag now)."""
         if not image_ids:
             return {}
         threshold = min(1.0, max(0.0, threshold))
@@ -169,8 +171,6 @@ class SuggestionService:
             sl = await self.for_image(image_id)
             for category, items in sl.by_category.items():
                 for s in items:
-                    if s.canonical_tag_id is None or s.creates_new_tag:
-                        continue
                     # for_image keeps rejected tags (flagged) for the rail;
                     # bulk consensus must still ignore them — a tag dismissed on
                     # an image isn't a suggestion for that image.