feat(ml): presentation auto-hide settings + review table (#141 step 3)

MLSettings gains presentation_auto_apply_enabled / _threshold (default 0.90) +
presentation_conflict_threshold (default 0.50): banner/editor auto-hide with a
FLAT threshold (decoupled from content-head graduation), plus the "also looks
like content" conflict cut. New presentation_review table (image, presentation
tag, conflict tag + score, created/resolved_at) records auto-hides flagged for
review. Migration 0082 (columns + table), ml_admin API (editable + get_settings
+ _validate bounds), settings roundtrip/bounds test. The sweep that reads these
knobs + the Settings UI land in step 4.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDgx8bQS5YrGRK76v8HUnM

backend/app/api/ml_admin.py

@@ -39,6 +39,9 @@ _EDITABLE = (
     "ccip_match_threshold",
     "ccip_auto_apply_enabled",
     "ccip_auto_apply_threshold",
+    "presentation_auto_apply_enabled",
+    "presentation_auto_apply_threshold",
+    "presentation_conflict_threshold",
     "embedder_model_name",
     "embedder_model_version",
     *_DETECTOR_FIELDS,
@@ -96,6 +99,9 @@ async def get_settings():
             "ccip_match_threshold": s.ccip_match_threshold,
             "ccip_auto_apply_enabled": s.ccip_auto_apply_enabled,
             "ccip_auto_apply_threshold": s.ccip_auto_apply_threshold,
+            "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,
             "embedder_model_name": s.embedder_model_name,
             **{f: getattr(s, f) for f in _DETECTOR_FIELDS},
         }
@@ -150,6 +156,12 @@ def _validate(p: dict) -> str | None:
         return "ccip_match_threshold must be between 0.5 and 0.999"
     if not (0.5 <= float(p["ccip_auto_apply_threshold"]) <= 0.999):
         return "ccip_auto_apply_threshold must be between 0.5 and 0.999"
+    # Presentation chrome auto-hide (#141). Auto-apply runs high (hiding is
+    # consequential); the conflict cut is a plain probability [0,1].
+    if not (0.5 <= float(p["presentation_auto_apply_threshold"]) <= 0.999):
+        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"
     # 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"):