feat(ml): CCIP references exclude unconfirmed auto character tags + confirm trips detectors (m139)

Completes "no self-training": unconfirmed auto-applied character tags no longer
seed CCIP references — character_references + the prototype builder
(_current_fingerprints/_rebuild_one) gain a shared _positive_char_tag filter
(human-applied OR operator-confirmed), mirroring the head-positive exclusion.

Confirming a tag also has to move the change-detectors, or an incremental
refresh/Retrain right after a confirm wouldn't fold the tag in (only the nightly
full pass would): the CCIP global gate now counts character confirmations, and
the head training fingerprint counts confirmations. Test for the CCIP path.

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

tests/test_character_prototypes.py

@@ -12,6 +12,7 @@ from backend.app.models import (
     MLSettings,
     Tag,
     TagKind,
+    TagPositiveConfirmation,
 )
 from backend.app.models.tag import image_tag
 from backend.app.services.ml.character_prototypes import (
@@ -141,6 +142,27 @@ def test_multi_character_image_not_referenced(db_sync):
     assert _proto_count(db_sync, daphne.id) == 0
 
 
+def test_unconfirmed_auto_char_tag_not_referenced(db_sync):
+    # A single-character image whose ONLY character tag was AUTO-applied
+    # (unconfirmed) must NOT seed a prototype — else CCIP self-trains on its own
+    # guess (milestone 139). Confirming it (which trips the global gate) makes it
+    # a reference.
+    raven = _char(db_sync, "Raven")
+    img = _img(db_sync, "z" * 64)
+    _figure(db_sync, img.id)
+    db_sync.execute(image_tag.insert().values(
+        image_record_id=img.id, tag_id=raven.id, source="ccip_auto",
+    ))
+    db_sync.commit()
+    refresh_character_prototypes(db_sync)
+    assert _proto_count(db_sync, raven.id) == 0
+
+    db_sync.add(TagPositiveConfirmation(image_record_id=img.id, tag_id=raven.id))
+    db_sync.commit()
+    refresh_character_prototypes(db_sync)
+    assert _proto_count(db_sync, raven.id) == 1
+
+
 def test_lost_references_are_removed(db_sync):
     raven = _char(db_sync, "Raven")
     img = _img(db_sync, "e" * 64)