fix(test-infra): openInboundDb honors in-memory test DB

initTestSessionDb() creates an in-memory inbound singleton, but
openInboundDb() always opened the hardcoded /workspace/inbound.db
path. Every test that exercised getPendingMessages — directly, or via
test fixtures that load data through it (e.g. poll-loop.test.ts:29
loads formatter test rows via getPendingMessages) — failed with
SQLITE_CANTOPEN under `bun test` outside a real container.

Baseline on main: 34 pass, 25 fail across 6 files. After this fix:
59 pass, 0 fail.

In test mode, openInboundDb returns the in-memory singleton. The
singleton's .close() is no-op'd in initTestSessionDb so caller
try/finally cleanup doesn't tear down the shared DB; closeSessionDb
invokes the saved original close to do the real teardown.

Production behavior is unchanged — _inboundIsTest only flips inside
initTestSessionDb, which is never called outside the test runner.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -27,6 +27,13 @@ const DEFAULT_HEARTBEAT_PATH = '/workspace/.heartbeat';
 let _inbound: Database | null = null;
 let _outbound: Database | null = null;
 let _heartbeatPath: string = DEFAULT_HEARTBEAT_PATH;
+// True when initTestSessionDb() set _inbound to an in-memory DB. Used by
+// openInboundDb() so tests don't try to open the missing /workspace path.
+let _inboundIsTest = false;
+// Saved real close() for the in-memory inbound singleton. We no-op the
+// public .close() during tests so caller try/finally doesn't tear down
+// the shared DB; closeSessionDb() invokes this to do the real teardown.
+let _inboundOriginalClose: (() => void) | null = null;
 
 /**
  * Avoid all cached db reads; open inbound.db read-only with mmap and page cache disabled. 
@@ -42,6 +49,12 @@ let _heartbeatPath: string = DEFAULT_HEARTBEAT_PATH;
  * Cost is microseconds per query, so safe for universal use.
  */
 export function openInboundDb(): Database {
+  // In test mode the inbound DB is an in-memory singleton — there is no
+  // file at DEFAULT_INBOUND_PATH. Return the singleton directly; its
+  // .close() was no-op'd in initTestSessionDb so caller try/finally
+  // cleanup doesn't tear down the shared DB.
+  if (_inboundIsTest && _inbound) return _inbound;
+
   const db = new Database(DEFAULT_INBOUND_PATH, { readonly: true });
   db.exec('PRAGMA busy_timeout = 5000');
   db.exec('PRAGMA mmap_size = 0');
@@ -171,6 +184,12 @@ export function clearStaleProcessingAcks(): void {
 /** For tests — creates in-memory DBs with the session schemas. */
 export function initTestSessionDb(): { inbound: Database; outbound: Database } {
   _inbound = new Database(':memory:');
+  _inboundIsTest = true;
+  // No-op .close() so callers using openInboundDb()'s try/finally pattern
+  // don't tear down our shared singleton. closeSessionDb() does the real
+  // teardown via the saved original.
+  _inboundOriginalClose = _inbound.close.bind(_inbound);
+  _inbound.close = () => {};
   _inbound.exec('PRAGMA foreign_keys = ON');
   _inbound.exec(`
     CREATE TABLE messages_in (
@@ -244,8 +263,14 @@ export function initTestSessionDb(): { inbound: Database; outbound: Database } {
 }
 
 export function closeSessionDb(): void {
-  _inbound?.close();
+  if (_inboundOriginalClose) {
+    _inboundOriginalClose();
+    _inboundOriginalClose = null;
+  } else {
+    _inbound?.close();
+  }
   _inbound = null;
+  _inboundIsTest = false;
   _outbound?.close();
   _outbound = null;
 }