fix(memory): ScreenMemory threshold hardening + stale layout purge (P0-3)

- Raised similarity_threshold from 0.90 to 0.95 in get_screen_type() to eliminate
  POST_DETAIL false-positives caused by embedding saturation.
- Implemented purge_stale_screens() with 24h TTL to remove layout drift.
- Added collection size cap (200 points) to store_screen() with automatic wipe
  when saturated to clear overfitting bias.
- Triggered purge_stale_screens() on ScreenIdentity initialization.

TDD: 3 new tests for threshold defaults and purge method integrity.

GramAddict/core/perception/screen_identity.py

@@ -40,6 +40,8 @@ class ScreenIdentity:
             from GramAddict.core.qdrant_memory import ScreenMemoryDB
 
             self.screen_memory = ScreenMemoryDB()
+            if self.screen_memory:
+                self.screen_memory.purge_stale_screens()
         except ImportError:
             self.screen_memory = None
 

GramAddict/core/qdrant_memory.py

@@ -772,6 +772,16 @@ class ScreenMemoryDB(QdrantBase):
         if not vector:
             return
 
+        # ── P0-3: Collection Management ──
+        # Prevent embedding saturation by limiting to 200 high-quality signatures
+        try:
+            count = self.client.count(collection_name=self.collection_name).count
+            if count >= 200:
+                logger.warning("🚨 [ScreenMemory] Collection saturated (>= 200). Wiping to clear overfitting bias.")
+                self.wipe_collection()
+        except Exception:
+            pass
+
         self.upsert_point(
             seed_string=xml_signature,
             vector=vector,
@@ -783,7 +793,7 @@ class ScreenMemoryDB(QdrantBase):
             log_success=f"🧠 [ScreenMemory] Learned new layout mapping: {screen_type}",
         )
 
-    def get_screen_type(self, xml_signature: str, similarity_threshold: float = 0.90) -> Optional[str]:
+    def get_screen_type(self, xml_signature: str, similarity_threshold: float = 0.95) -> Optional[str]:
         if not self.is_connected or not xml_signature:
             return None
 
@@ -809,6 +819,30 @@ class ScreenMemoryDB(QdrantBase):
             logger.debug(f"Screen memory error: {e}")
             return None
 
+    def purge_stale_screens(self, max_age_hours: float = 24):
+        """Removes entries older than max_age_hours to prevent layout drift poisoning."""
+        if not self.is_connected:
+            return
+        try:
+            points, _ = self.client.scroll(
+                collection_name=self.collection_name,
+                limit=200,
+                with_payload=True,
+            )
+            now = time.time()
+            purged = 0
+            for pt in points:
+                payload = pt.payload or {}
+                stored_at = payload.get("stored_at", 0)
+                age_hours = (now - stored_at) / 3600 if stored_at > 0 else 0
+                if age_hours > max_age_hours:
+                    self.delete_point(payload.get("signature", str(pt.id)))
+                    purged += 1
+            if purged:
+                logger.info(f"🧹 [ScreenMemory] Purged {purged} stale layout mappings (> {max_age_hours}h).")
+        except Exception as e:
+            logger.debug(f"Screen purge error: {e}")
+
     def purge_screen(self, xml_signature: str):
         """Unlearns a screen classification to recover from hallucinations."""
         if not self.is_connected or not xml_signature: