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/services/gallery_service.py

@@ -31,7 +31,7 @@ from ..models import (
     Tag,
     TagPositiveConfirmation,
 )
-from ..models.tag import PRESENTATION_SYSTEM_TAGS, WIP_SYSTEM_TAG, image_tag
+from ..models.tag import CHROME_SYSTEM_TAGS, PROCESS_SYSTEM_TAGS, image_tag
 from .pagination import decode_cursor, encode_cursor
 from .tag_query import (
     fandom_join_alias,
@@ -419,16 +419,17 @@ class GalleryService:
     async def _hidden_tag_ids(
         self, include_hidden, tag_ids, tag_or_groups,
     ) -> list[int] | None:
-        """Presentation-chrome tag ids to implicitly exclude from a gallery query,
-        or None. None when the caller asked to include hidden, when the operator
-        is explicitly filtering FOR a presentation tag (they clearly want to see
-        it), or when no presentation tags exist. (milestone 141)"""
+        """Chrome (banner) tag ids to implicitly exclude from a gallery query, or
+        None. None when the caller asked to include hidden, when the operator is
+        explicitly filtering FOR a chrome tag (they clearly want to see it), or when
+        no chrome tags exist. (milestone 141; #1464: editor screenshot is now PROCESS
+        — shown — so only `banner` hides here.)"""
         if include_hidden:
             return None
         rows = await self.session.execute(
             select(Tag.id).where(
                 Tag.is_system.is_(True),
-                Tag.name.in_(PRESENTATION_SYSTEM_TAGS),
+                Tag.name.in_(CHROME_SYSTEM_TAGS),
             )
         )
         pres = [r[0] for r in rows]
@@ -749,15 +750,16 @@ class GalleryService:
         eff = _effective_date_col()
         stmt = select(ImageRecord, Post.post_date, eff.label("eff"))
         stmt = _outer_join_primary_post(stmt)
-        # Presentation images (banner / editor-screenshot system tags, #128)
-        # cluster on UI chrome rather than content, so near any one of them
-        # they'd fill the grid. Excluded from CANDIDATES only — the anchor
-        # itself may be a banner. `wip` stays surfaced here by default (real art;
-        # only the training pipelines exclude it), but the Explore rabbit-hole
-        # passes exclude_wip to also drop work-in-progress (operator, 2026-07-08).
-        excluded_system_tags = PRESENTATION_SYSTEM_TAGS
+        # Chrome (banner, #128) clusters on UI rather than content, so near any one
+        # of them they'd fill the grid → excluded from CANDIDATES always (the anchor
+        # itself may be a banner). PROCESS art (wip / editor screenshot) stays
+        # surfaced here by default (real content; only the training pipelines exclude
+        # it), but the Explore rabbit-hole passes exclude_wip to also drop the whole
+        # process group so a browse doesn't keep surfacing work-in-progress
+        # (operator, 2026-07-08; #1464 — editor now rides with wip here).
+        excluded_system_tags = CHROME_SYSTEM_TAGS
         if exclude_wip:
-            excluded_system_tags = (*PRESENTATION_SYSTEM_TAGS, WIP_SYSTEM_TAG)
+            excluded_system_tags = (*CHROME_SYSTEM_TAGS, *PROCESS_SYSTEM_TAGS)
         presentation = (
             select(image_tag.c.image_record_id)
             .join(Tag, Tag.id == image_tag.c.tag_id)