Add deduplication to store_memory

Before inserting, check if a near-identical memory exists (cosine > 0.85).
If found, skip insert. Prevents flooding the DB with repeated facts
from the same conversation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

memory.py

@@ -25,6 +25,16 @@ async def store_memory(content: str, user_id: str = "default",
     pool = await get_pool()
     vec = await embed(content)
     async with pool.acquire() as conn:
+        # skip if near-duplicate already exists (cosine > 0.85)
+        existing = await conn.fetchval("""
+            SELECT id FROM memories
+            WHERE user_id = $1
+              AND (metadata->>'archived') IS NULL
+              AND 1 - (embedding <=> $2::vector) > 0.85
+            LIMIT 1
+        """, user_id, _vec_str(vec))
+        if existing:
+            return
         await conn.execute("""
             INSERT INTO memories (user_id, content, embedding, importance, memory_type, metadata)
             VALUES ($1, $2, $3::vector, $4, $5, $6)