fix: migration 009 add source_count + entity dedup index

- Add source_count INTEGER DEFAULT 1 column
- Dedup existing rows before creating unique index
- CREATE UNIQUE INDEX idx_memory_entity_project_name (project_id, name)
- Idempotent: safe to re-run

crates/mem-store/migrations/009_temporal_edge_migration.sql

@@ -47,8 +47,20 @@ CREATE INDEX IF NOT EXISTS idx_memory_edge_target ON memory_edge(target_id);
 CREATE INDEX IF NOT EXISTS idx_memory_edge_project ON memory_edge(project_id);
 CREATE INDEX IF NOT EXISTS idx_memory_edge_relation ON memory_edge(relation_type);
 
--- Ensure memory_entity has deleted_at for BFS soft-delete queries
+-- Ensure memory_entity has all columns code expects
 ALTER TABLE memory_entity ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
+ALTER TABLE memory_entity ADD COLUMN IF NOT EXISTS source_count INTEGER DEFAULT 1;
+
+-- Unique constraint for entity upsert dedup
+DO $$
+BEGIN
+    -- Dedup existing rows before creating unique index
+    DELETE FROM memory_entity a USING memory_entity b
+    WHERE a.project_id = b.project_id AND a.name = b.name
+      AND a.t_created < b.t_created;
+EXCEPTION WHEN OTHERS THEN NULL;
+END $$;
+CREATE UNIQUE INDEX IF NOT EXISTS idx_memory_entity_project_name ON memory_entity(project_id, name);
 
 -- ROLLBACK instructions:
 -- DROP TABLE IF EXISTS memory_edge;