feat(session): persist model tier overrides per session

Store per-session config in SQLite and route /model and /reset through command fast-paths so channel sessions keep independent model selection across reconnects and restarts.

src/session/manager.test.ts

@@ -58,4 +58,37 @@ describe('SessionManager', () => {
     expect(sessions).toContain('telegram:user-123');
     expect(sessions).toContain('tui:local');
   });
+
+  it('indexes and searches history when enabled', () => {
+    manager = new SessionManager(store, {
+      enabled: true,
+      maxKeywords: 8,
+      searchLimit: 10,
+      minScore: 0.1,
+    });
+
+    const session = manager.getSession('telegram', 'user-123');
+    session.addMessage({ role: 'user', content: 'deploy backend api' });
+
+    const results = manager.searchHistory('deploy backend');
+    expect(results.length).toBeGreaterThan(0);
+    expect(results[0].sessionId).toBe('telegram:user-123');
+  });
+
+  it('reindexHistory is safe and idempotent', () => {
+    manager = new SessionManager(store, {
+      enabled: true,
+      maxKeywords: 8,
+      searchLimit: 10,
+      minScore: 0.1,
+    });
+
+    const session = manager.getSession('telegram', 'user-abc');
+    session.addMessage({ role: 'user', content: 'history indexing test' });
+
+    const first = manager.reindexHistory();
+    const second = manager.reindexHistory();
+    expect(first).toBeGreaterThan(0);
+    expect(second).toBe(first);
+  });
 });