feat(system-tags): process vs chrome groups + WIP provisional auto-apply (#1464)

Backend for the system-tag behavior refactor (milestone #157). editor screenshot
moves from chrome (hidden) to the PROCESS group (shown, like wip); wip+editor gain
provisional auto-apply so they stop needing endless manual identification —
without a runaway loop.

- tag.py: split PRESENTATION_SYSTEM_TAGS → CHROME_SYSTEM_TAGS (banner) +
  PROCESS_SYSTEM_TAGS (wip, editor screenshot).
- heads.py: generalize presentation_auto_apply_sweep → system_tag_auto_apply_sweep
  (mode chrome|process). Same Guard 1 (skip human/confirmed) + Guard 2 (ring-loud
  conflict → PresentationReview). process mode uses source 'process_auto' and does
  NOT hide (hide is a gallery-query effect of group membership).
- training_data._AUTO_SOURCES += 'process_auto' → the head never trains on its own
  auto-applied output; only wip_title/manual train it (the runaway break).
- ml_settings: process_auto_apply_enabled (OFF, opt-in) + threshold + conflict
  threshold. presentation_review.mode ('chrome'|'process'). Migration 0086.
- gallery_service: default-hide reads CHROME only (editor now shows); Explore
  neighbors exclude the whole PROCESS group.
- tasks/ml + celery beat: scheduled_process_auto_apply (daily, opt-in); prune
  covers both modes.
- api: ml_admin process_* CRUD+validation; hidden-review returns mode.
- tests: rename chrome sweep calls; new test_process_auto_apply (apply, guards,
  mode flag, no-self-train); gallery test asserts editor now visible.

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

backend/app/tasks/ml.py

@@ -599,15 +599,33 @@ def scheduled_ccip_auto_apply() -> str:
     soft_time_limit=1800, time_limit=2100,
 )
 def scheduled_presentation_auto_apply() -> str:
-    """Auto-hide presentation chrome (banner / editor screenshot) on a daily
-    passive sweep (#141). No-op unless presentation_auto_apply_enabled. Idempotent
-    — already-hidden images are skipped — so an interrupted run simply re-runs next
-    cycle (that IS the recovery). Wall-clock bounded by the task time limits."""
-    from ..services.ml.heads import presentation_auto_apply_sweep
+    """Auto-hide presentation chrome (banner) on a daily passive sweep (#141).
+    No-op unless presentation_auto_apply_enabled. Idempotent — already-tagged images
+    are skipped — so an interrupted run simply re-runs next cycle (that IS the
+    recovery). Wall-clock bounded by the task time limits."""
+    from ..services.ml.heads import system_tag_auto_apply_sweep
 
     SessionLocal = _sync_session_factory()
     with SessionLocal() as session:
-        result = presentation_auto_apply_sweep(session)
+        result = system_tag_auto_apply_sweep(session, mode="chrome")
+    return f"applied={result['n_applied']} flagged={result['n_flagged']}"
+
+
+@celery.task(
+    name="backend.app.tasks.ml.scheduled_process_auto_apply",
+    soft_time_limit=1800, time_limit=2100,
+)
+def scheduled_process_auto_apply() -> str:
+    """Auto-apply the PROCESS system tags (wip / editor screenshot) on a daily
+    passive sweep (#1464) — provisional source, ring-loud review guard, image stays
+    VISIBLE. No-op unless process_auto_apply_enabled (opt-in). Idempotent —
+    already-tagged/rejected images are skipped — so an interrupted run just re-runs
+    next cycle (the recovery). Wall-clock bounded by the task time limits."""
+    from ..services.ml.heads import system_tag_auto_apply_sweep
+
+    SessionLocal = _sync_session_factory()
+    with SessionLocal() as session:
+        result = system_tag_auto_apply_sweep(session, mode="process")
     return f"applied={result['n_applied']} flagged={result['n_flagged']}"