feat: retire the sketch/doodle WIP title tier, and the review strip asks "Is this a WIP?" (milestone 430)

The soft tier (#1474) tagged `wip` on any post titled sketch, doodle or
scribble: 6,096 of the library's 8,876 wip tags. Its conflict audit flagged
most of them, because finished art scores >= 0.5 on some content head,
which filled the Gallery strip with 2,086 cards. A "sketch" is usually
finished work, so the operator retired the tier. The artist's own
"WIP" / "work in progress" title rule and human wip tags stay.

- Removed: the soft matcher, source and prefilter; the importer and backfill
  soft branches; soft_wip_conflict_audit with its task and beat; the
  wip_soft_title_tagging_enabled setting, API field and toggle; and
  wip_title_soft from _AUTO_SOURCES.
- Migration 0112: a soft tag the operator confirmed, or kept from the strip,
  becomes `manual`. Every other soft tag is deleted, along with the open
  review cards whose tag is gone. The column is dropped.
- Review strip (#4424): each card asks "Is this a WIP?" (or banner, and so on),
  and the buttons read "Is a WIP" / "Is not a WIP". The content tag it also
  scored on is shown as the reason it was flagged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

backend/app/services/importer.py

@@ -49,10 +49,8 @@ from .audits import single_color
 from .link_extract import extract_external_links
 from .thumbnailer import Thumbnailer
 from .wip_title import (
-    WIP_TITLE_SOFT_SOURCE,
     WIP_TITLE_SOURCE,
     apply_wip_image_tags,
-    matches_soft_wip_title,
     matches_wip_title,
     resolve_wip_tag_id,
 )
@@ -1040,9 +1038,7 @@ class Importer:
         removal sticks. The existing catalogue is covered separately by the
         operator-triggered backfill sweep. Gated by the settings toggle, and
         best-effort: any failure is logged, never allowed to fail the import."""
-        hard_on = self.settings.wip_title_tagging_enabled
-        soft_on = self.settings.wip_soft_title_tagging_enabled
-        if not (hard_on or soft_on):
+        if not self.settings.wip_title_tagging_enabled:
             return
         if record.primary_post_id is None:
             return
@@ -1050,21 +1046,14 @@ class Importer:
             title = self.session.execute(
                 select(Post.post_title).where(Post.id == record.primary_post_id)
             ).scalar_one_or_none()
-            # HARD tier ("WIP"/"work in progress") wins — higher precision, and it
-            # trains the head; SOFT (sketch/doodle, #1474) is the provisional fallback
-            # that never trains (source wip_title_soft).
-            if hard_on and matches_wip_title(title):
-                source = WIP_TITLE_SOURCE
-            elif soft_on and matches_soft_wip_title(title):
-                source = WIP_TITLE_SOFT_SOURCE
-            else:
+            if not matches_wip_title(title):
                 return
             if self._wip_tag_id is _UNSET:
                 self._wip_tag_id = resolve_wip_tag_id(self.session)
             if self._wip_tag_id is None:
                 return
             apply_wip_image_tags(
-                self.session, [record.id], self._wip_tag_id, source=source
+                self.session, [record.id], self._wip_tag_id, source=WIP_TITLE_SOURCE
             )
         except Exception as exc:  # noqa: BLE001 — a tag must never fail an import
             log.warning(