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

backend/app/services/ml/ccip.py

@@ -13,7 +13,7 @@ exact CCIP difference metric/threshold gets validated against the model during
 the hands-on eval. numpy is imported lazily (API worker has it via pgvector).
 """
 
-from sqlalchemy import func, select
+from sqlalchemy import exists, func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from ...models import (
@@ -23,8 +23,10 @@ from ...models import (
     MLSettings,
     Tag,
     TagKind,
+    TagPositiveConfirmation,
 )
 from ...models.tag import image_tag
+from .training_data import _AUTO_SOURCES
 
 # Cosine-similarity floor to call a figure the same character. The live setting
 # (ml_settings.ccip_match_threshold) drives it; this is only the fallback when no
@@ -111,6 +113,17 @@ async def _ref_signature(session: AsyncSession) -> tuple:
     return (n_tags, n_regs, max_id, n_hygiene)
 
 
+def _positive_char_tag():
+    """Condition on the joined character image_tag: HUMAN-applied or operator-
+    confirmed — NOT an unconfirmed auto-apply. Keeps an auto-tagged character from
+    self-seeding CCIP references, so a ccip_auto misfire can't reinforce itself
+    (milestone 139) — mirrors the head-training positive exclusion."""
+    return image_tag.c.source.not_in(_AUTO_SOURCES) | exists().where(
+        TagPositiveConfirmation.image_record_id == image_tag.c.image_record_id,
+        TagPositiveConfirmation.tag_id == image_tag.c.tag_id,
+    )
+
+
 async def character_references(session: AsyncSession) -> dict[int, list]:
     """Per character-tag CCIP reference vectors: figure/face-region CCIP
     embeddings on UNAMBIGUOUS (single-character) images carrying that tag.
@@ -128,6 +141,7 @@ async def character_references(session: AsyncSession) -> dict[int, list]:
             )
             .join(Tag, Tag.id == image_tag.c.tag_id)
             .where(Tag.kind == TagKind.character)
+            .where(_positive_char_tag())
             .where(ImageRegion.kind.in_(_FIGURE_KINDS))
             .where(ImageRegion.ccip_embedding.is_not(None))
             .where(ImageRegion.image_record_id.in_(_single_character_images()))