feat: async significance pass with auto-pin on score 3

chat/state/memory.py

@@ -38,6 +38,35 @@ def _apply_memory_written(conn: Connection, e: Event) -> None:
     )
 
 
+@on("memory_significance_set")
+def _apply_memory_significance_set(conn: Connection, e: Event) -> None:
+    """Update an existing memory's significance score (T22).
+
+    Emitted by the async significance worker after it scores the turn.
+    """
+    p = e.payload
+    conn.execute(
+        "UPDATE memories SET significance = ? WHERE id = ?",
+        (int(p["significance"]), int(p["memory_id"])),
+    )
+
+
+@on("memory_pin_changed")
+def _apply_memory_pin_changed(conn: Connection, e: Event) -> None:
+    """Toggle a memory's pin state (T22, §8.5).
+
+    Used both for auto-pinning a pivotal turn and for evicting the oldest
+    auto-pin when the per-owner soft cap is exceeded. Manual pins use the
+    same handler; the ``auto_pinned`` flag distinguishes them so the
+    eviction query can leave manual pins alone.
+    """
+    p = e.payload
+    conn.execute(
+        "UPDATE memories SET pinned = ?, auto_pinned = ? WHERE id = ?",
+        (int(p["pinned"]), int(p["auto_pinned"]), int(p["memory_id"])),
+    )
+
+
 def get_memory(conn: Connection, memory_id: int) -> dict | None:
     row = conn.execute(
         "SELECT * FROM memories WHERE id = ?", (memory_id,)