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/store.ts

@@ -1,6 +1,7 @@
 import Database from 'better-sqlite3';
 import type { Message } from '../models/types.js';
 import type { PairingStore, ApprovedSender } from '../channels/pairing.js';
+import type { HistoryMetadata } from './indexer.js';
 
 /** Parse a duration string like '30d', '7d', '12h' to milliseconds. Returns null if invalid or '0'. */
 export function parseDuration(s: string): number | null {
@@ -44,13 +45,18 @@ export class SessionStore {
       );
       CREATE INDEX IF NOT EXISTS idx_session_config_session ON session_config(session_id);
     `);
+
+    const messageColumns = this.db.prepare('PRAGMA table_info(messages)').all() as Array<{ name: string }>;
+    if (!messageColumns.some(column => column.name === 'metadata')) {
+      this.db.exec('ALTER TABLE messages ADD COLUMN metadata TEXT');
+    }
   }
 
-  addMessage(sessionId: string, message: Message): void {
+  addMessage(sessionId: string, message: Message, metadata?: HistoryMetadata): void {
     const stmt = this.db.prepare(
-      'INSERT INTO messages (session_id, role, content) VALUES (?, ?, ?)',
+      'INSERT INTO messages (session_id, role, content, metadata) VALUES (?, ?, ?, ?)',
     );
-    stmt.run(sessionId, message.role, message.content);
+    stmt.run(sessionId, message.role, message.content, metadata ? JSON.stringify(metadata) : null);
   }
 
   getMessages(sessionId: string): Message[] {
@@ -75,10 +81,10 @@ export class SessionStore {
       this.db.prepare('DELETE FROM messages WHERE session_id = ?').run(sessionId);
       // Re-insert in order
       const insert = this.db.prepare(
-        'INSERT INTO messages (session_id, role, content) VALUES (?, ?, ?)',
+        'INSERT INTO messages (session_id, role, content, metadata) VALUES (?, ?, ?, ?)',
       );
       for (const msg of messages) {
-        insert.run(sessionId, msg.role, msg.content);
+        insert.run(sessionId, msg.role, msg.content, null);
       }
     });
     transaction();
@@ -194,4 +200,68 @@ export class SessionStore {
   close(): void {
     this.db.close();
   }
+
+  getMessagesWithMetadata(sessionId: string): Array<{
+    id: number;
+    sessionId: string;
+    role: 'user' | 'assistant';
+    content: string;
+    createdAt: number;
+    metadata: HistoryMetadata | null;
+  }> {
+    const stmt = this.db.prepare(
+      'SELECT id, session_id, role, content, created_at, metadata FROM messages WHERE session_id = ? ORDER BY id ASC',
+    );
+    const rows = stmt.all(sessionId) as Array<{
+      id: number;
+      session_id: string;
+      role: string;
+      content: string;
+      created_at: number;
+      metadata: string | null;
+    }>;
+
+    return rows.map(row => ({
+      id: row.id,
+      sessionId: row.session_id,
+      role: row.role as 'user' | 'assistant',
+      content: row.content,
+      createdAt: row.created_at,
+      metadata: row.metadata ? JSON.parse(row.metadata) as HistoryMetadata : null,
+    }));
+  }
+
+  getAllMessagesWithMetadata(): Array<{
+    id: number;
+    sessionId: string;
+    role: 'user' | 'assistant';
+    content: string;
+    createdAt: number;
+    metadata: HistoryMetadata | null;
+  }> {
+    const stmt = this.db.prepare(
+      'SELECT id, session_id, role, content, created_at, metadata FROM messages ORDER BY id ASC',
+    );
+    const rows = stmt.all() as Array<{
+      id: number;
+      session_id: string;
+      role: string;
+      content: string;
+      created_at: number;
+      metadata: string | null;
+    }>;
+
+    return rows.map(row => ({
+      id: row.id,
+      sessionId: row.session_id,
+      role: row.role as 'user' | 'assistant',
+      content: row.content,
+      createdAt: row.created_at,
+      metadata: row.metadata ? JSON.parse(row.metadata) as HistoryMetadata : null,
+    }));
+  }
+
+  updateMessageMetadata(messageId: number, metadata: HistoryMetadata): void {
+    this.db.prepare('UPDATE messages SET metadata = ? WHERE id = ?').run(JSON.stringify(metadata), messageId);
+  }
 }