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/api/ml_admin.py

@@ -42,6 +42,9 @@ _EDITABLE = (
     "presentation_auto_apply_enabled",
     "presentation_auto_apply_threshold",
     "presentation_conflict_threshold",
+    "process_auto_apply_enabled",
+    "process_auto_apply_threshold",
+    "process_conflict_threshold",
     "embedder_model_name",
     "embedder_model_version",
     *_DETECTOR_FIELDS,
@@ -102,6 +105,9 @@ async def get_settings():
             "presentation_auto_apply_enabled": s.presentation_auto_apply_enabled,
             "presentation_auto_apply_threshold": s.presentation_auto_apply_threshold,
             "presentation_conflict_threshold": s.presentation_conflict_threshold,
+            "process_auto_apply_enabled": s.process_auto_apply_enabled,
+            "process_auto_apply_threshold": s.process_auto_apply_threshold,
+            "process_conflict_threshold": s.process_conflict_threshold,
             "embedder_model_name": s.embedder_model_name,
             **{f: getattr(s, f) for f in _DETECTOR_FIELDS},
         }
@@ -162,6 +168,12 @@ def _validate(p: dict) -> str | None:
         return "presentation_auto_apply_threshold must be between 0.5 and 0.999"
     if not (0.0 <= float(p["presentation_conflict_threshold"]) <= 1.0):
         return "presentation_conflict_threshold must be between 0 and 1"
+    # Process auto-apply (#1464). wip/editor stay VISIBLE so a false apply is
+    # low-harm (excludes-from-training + a review flag), but keep the same bar.
+    if not (0.5 <= float(p["process_auto_apply_threshold"]) <= 0.999):
+        return "process_auto_apply_threshold must be between 0.5 and 0.999"
+    if not (0.0 <= float(p["process_conflict_threshold"]) <= 1.0):
+        return "process_conflict_threshold must be between 0 and 1"
     # Embedder model swap (#1190): both must be non-empty. Changing them means a
     # different embedding space — the operator must re-embed + retrain after.
     for key in ("embedder_model_name", "embedder_model_version"):