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>

tests/test_presentation_auto_apply.py

@@ -15,7 +15,7 @@ from backend.app.models import (
 from backend.app.models.tag import image_tag
 from backend.app.services.ml.heads import (
     auto_apply_sweep,
-    presentation_auto_apply_sweep,
+    system_tag_auto_apply_sweep,
 )
 
 pytestmark = pytest.mark.integration
@@ -70,7 +70,7 @@ def test_presentation_sweep_hides_chrome(db_sync):
     _head(db_sync, banner.id, 0, weight=3.0)
     img = _img(db_sync, "a" * 64, _emb(0))
     db_sync.commit()
-    res = presentation_auto_apply_sweep(db_sync)
+    res = system_tag_auto_apply_sweep(db_sync, mode="chrome")
     assert res["n_applied"] == 1
     assert _source(db_sync, img.id, banner.id) == "presentation_auto"
 
@@ -86,7 +86,7 @@ def test_presentation_sweep_hard_skips_valued_image(db_sync):
     db_sync.execute(image_tag.insert().values(
         image_record_id=img.id, tag_id=content.id, source="manual"))
     db_sync.commit()
-    res = presentation_auto_apply_sweep(db_sync)
+    res = system_tag_auto_apply_sweep(db_sync, mode="chrome")
     assert res["n_applied"] == 0
     assert _source(db_sync, img.id, banner.id) is None
 
@@ -102,7 +102,7 @@ def test_presentation_sweep_flags_conflict(db_sync):
     _head(db_sync, content.id, 0, weight=1.0)     # content head also fires
     img = _img(db_sync, "c" * 64, _emb(0))
     db_sync.commit()
-    res = presentation_auto_apply_sweep(db_sync)
+    res = system_tag_auto_apply_sweep(db_sync, mode="chrome")
     assert res["n_applied"] == 1
     assert res["n_flagged"] == 1
     assert _source(db_sync, img.id, banner.id) == "presentation_auto"
@@ -123,7 +123,7 @@ def test_presentation_sweep_disabled_is_noop(db_sync):
     _head(db_sync, banner.id, 0, weight=3.0)
     img = _img(db_sync, "d" * 64, _emb(0))
     db_sync.commit()
-    res = presentation_auto_apply_sweep(db_sync)
+    res = system_tag_auto_apply_sweep(db_sync, mode="chrome")
     assert res["n_applied"] == 0
     assert _source(db_sync, img.id, banner.id) is None
 
@@ -134,7 +134,7 @@ def test_presentation_sweep_ignores_wip(db_sync):
     _head(db_sync, wip.id, 0, weight=3.0)
     img = _img(db_sync, "e" * 64, _emb(0))
     db_sync.commit()
-    res = presentation_auto_apply_sweep(db_sync)
+    res = system_tag_auto_apply_sweep(db_sync, mode="chrome")
     assert res["n_applied"] == 0
     assert _source(db_sync, img.id, wip.id) is None