feat(modal): autofocus tag input, expand general suggestions, retire copyright/artist categories

Four coupled operator-asked changes to the view modal (Scribe plan #509):

1. **Autofocus tag entry on modal open** — TagAutocomplete grabs focus
   in onMounted/nextTick so the caret is in the input the moment the
   modal renders. No click needed to start typing.

2. **General suggestions expanded by default** — SuggestionsPanel's
   general-category group now mounts with `:default-open="true"`.
   Operator can collapse if too noisy, but the v1 frame shows them.

3. **Lower general threshold default 0.95 → 0.50** — MLSettings.
   suggestion_threshold_general default matches character. Alembic
   0029 also bumps the existing singleton row's value if it's still
   at the old 0.95. Operator can re-tune from Settings → ML.

4. **Retire `copyright` + `artist` as ML suggestion categories** —
   neither feeds a Tag.kind (`artist` retired in FC-2d-vii-c, never
   really existed as a copyright tag-kind). They were surfaced in the
   suggestions pipeline + threshold settings UI but had no follow-
   through. Drop from SURFACED_CATEGORIES, suggestions._threshold_for,
   ml_admin GET/PATCH allowlist, MLSettings columns (alembic 0029
   drops the two columns), frontend CATEGORY_ORDER + CATEGORY_LABELS,
   SuggestionsPanel.peopleCats, AliasPickerDialog kind-check, and
   MLThresholdSliders rows.

Out of scope (intentional): `tag_kind` Postgres enum still includes
`artist` for historic Tag row queryability (per the model comment);
no operator pain reported, no enum-shrink needed.

Tests:
- test_surfaced_categories asserts {character, general}, excludes
  artist + copyright.
- test_threshold_for_artist_is_unsurfaced extended to cover copyright.
- test_get_and_patch_settings asserts new 0.50 default and the absent
  artist + copyright keys in the GET payload.

alembic/versions/0029_drop_artist_copyright_ml_thresholds.py

@@ -0,0 +1,71 @@
+"""drop artist + copyright ml thresholds; lower general default to 0.50
+
+Revision ID: 0029
+Revises: 0028
+Create Date: 2026-06-01
+
+Operator-flagged 2026-06-01: the view modal's Suggestions panel hides
+most general-category predictions because the default threshold is
+0.95. Lowering the default to 0.50 (matches character) so general
+suggestions surface more aggressively; the value remains tunable in
+Settings → ML.
+
+Same change retires two ML suggestion categories whose Tag.kind
+surfaces are unused:
+
+- `artist`: retired in FC-2d-vii-c — artist identity is acquisition-
+  derived (image_record.artist_id), never ML-inferred. The threshold
+  column was a leftover from before that retirement.
+- `copyright`: retired 2026-06-01 — the app uses `fandom` for the
+  franchise/copyright concept (per TagsView.vue's doc comment); no
+  Tag rows of kind=copyright exist, and the threshold column never
+  fed anything user-visible.
+
+Both columns are dropped from ml_settings; the existing row's
+suggestion_threshold_general value is bumped from 0.95 to 0.50 iff
+it's still at the old default, so deployed installs pick up the new
+UX without overriding any operator tuning.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+from sqlalchemy import text
+
+revision: str = "0029"
+down_revision: Union[str, None] = "0028"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Bump the general threshold for installs still at the old default.
+    op.execute(text(
+        "UPDATE ml_settings "
+        "SET suggestion_threshold_general = 0.50 "
+        "WHERE id = 1 AND suggestion_threshold_general = 0.95"
+    ))
+    op.drop_column("ml_settings", "suggestion_threshold_artist")
+    op.drop_column("ml_settings", "suggestion_threshold_copyright")
+
+
+def downgrade() -> None:
+    # Restore the columns with their prior defaults. The bump from
+    # 0.95 → 0.50 isn't reversible without remembering whether the
+    # operator had explicitly set 0.95 (unlikely — that was just the
+    # default) so we leave the current general value as-is.
+    from sqlalchemy import Column, Float
+
+    op.add_column(
+        "ml_settings",
+        Column(
+            "suggestion_threshold_artist",
+            Float, nullable=False, server_default="0.30",
+        ),
+    )
+    op.add_column(
+        "ml_settings",
+        Column(
+            "suggestion_threshold_copyright",
+            Float, nullable=False, server_default="0.50",
+        ),
+    )