v2 phase 1: foundation — types, DB layer, logging

Add the v2 data layer: typed interfaces, central DB with migration
runner, per-entity CRUD, and agent-runner session DB operations.

- src/log.ts: concise message-first logging API
- src/types-v2.ts: AgentGroup, MessagingGroup, Session, MessageIn/Out
- src/db/: connection (WAL), migration runner, 001-initial schema,
  CRUD for agent_groups, messaging_groups, sessions, pending_questions
- container/agent-runner/src/db/: session DB connection, messages_in
  reads + status transitions, messages_out writes
- 31 new tests, all 277 tests pass

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

container/agent-runner/src/db/connection.ts

@@ -0,0 +1,55 @@
+import Database from 'better-sqlite3';
+
+const SESSION_DB_PATH = '/workspace/session.db';
+
+let _db: Database.Database | null = null;
+
+export function getSessionDb(): Database.Database {
+  if (!_db) {
+    _db = new Database(process.env.SESSION_DB_PATH || SESSION_DB_PATH);
+    _db.pragma('journal_mode = WAL');
+    _db.pragma('foreign_keys = ON');
+  }
+  return _db;
+}
+
+/** For tests — opens an in-memory DB with session schema. */
+export function initTestSessionDb(): Database.Database {
+  _db = new Database(':memory:');
+  _db.pragma('foreign_keys = ON');
+  _db.exec(`
+    CREATE TABLE messages_in (
+      id             TEXT PRIMARY KEY,
+      kind           TEXT NOT NULL,
+      timestamp      TEXT NOT NULL,
+      status         TEXT DEFAULT 'pending',
+      status_changed TEXT,
+      process_after  TEXT,
+      recurrence     TEXT,
+      tries          INTEGER DEFAULT 0,
+      platform_id    TEXT,
+      channel_type   TEXT,
+      thread_id      TEXT,
+      content        TEXT NOT NULL
+    );
+    CREATE TABLE messages_out (
+      id             TEXT PRIMARY KEY,
+      in_reply_to    TEXT,
+      timestamp      TEXT NOT NULL,
+      delivered      INTEGER DEFAULT 0,
+      deliver_after  TEXT,
+      recurrence     TEXT,
+      kind           TEXT NOT NULL,
+      platform_id    TEXT,
+      channel_type   TEXT,
+      thread_id      TEXT,
+      content        TEXT NOT NULL
+    );
+  `);
+  return _db;
+}
+
+export function closeSessionDb(): void {
+  _db?.close();
+  _db = null;
+}