feat: memory schema with witness flags and FTS5 index

chat/db/migrations/0006_memories.sql

@@ -0,0 +1,35 @@
+CREATE TABLE memories (
+    id INTEGER PRIMARY KEY,
+    owner_id TEXT NOT NULL,
+    chat_id TEXT NOT NULL,
+    scene_id INTEGER,
+    pov_summary TEXT NOT NULL,
+    witness_you INTEGER NOT NULL,
+    witness_host INTEGER NOT NULL,
+    witness_guest INTEGER NOT NULL,
+    chat_clock_at TEXT,
+    source TEXT,
+    reliability REAL NOT NULL DEFAULT 1.0,
+    significance INTEGER NOT NULL DEFAULT 1,
+    pinned INTEGER NOT NULL DEFAULT 0,
+    auto_pinned INTEGER NOT NULL DEFAULT 0,
+    created_at TEXT NOT NULL DEFAULT (datetime('now'))
+);
+CREATE INDEX idx_memories_owner ON memories(owner_id);
+
+CREATE VIRTUAL TABLE memories_fts USING fts5(
+    pov_summary, content='memories', content_rowid='id'
+);
+
+CREATE TRIGGER memories_ai AFTER INSERT ON memories BEGIN
+    INSERT INTO memories_fts(rowid, pov_summary) VALUES (new.id, new.pov_summary);
+END;
+CREATE TRIGGER memories_au AFTER UPDATE ON memories BEGIN
+    INSERT INTO memories_fts(memories_fts, rowid, pov_summary)
+        VALUES('delete', old.id, old.pov_summary);
+    INSERT INTO memories_fts(rowid, pov_summary) VALUES (new.id, new.pov_summary);
+END;
+CREATE TRIGGER memories_ad AFTER DELETE ON memories BEGIN
+    INSERT INTO memories_fts(memories_fts, rowid, pov_summary)
+        VALUES('delete', old.id, old.pov_summary);
+END;