fix(picker): keep the worker-boundary mock off the vitest IPC channel

The mocked process.send consumed vitest's own fork-pool IPC messages and immediately ran the post callback, whose disconnect() severed the test worker's channel (process.connected is true under forks) — the whole spec's results vanished and win32-dialog-bindings.ts/win32-dialog-worker.ts fell to near-zero coverage on CI. The mock now records without invoking the callback or disconnecting; the real close lifecycle stays with built-worker.e2e.ts. Verified under both the threads and forks pools.

packages/host/directory-picker-native/tests/win32-dialog-bindings.spec.ts

@@ -271,9 +271,13 @@ describe('the worker entry over a mocked process boundary', () => {
   const installBoundary = (): { posted: { kind: string; message?: string }[] } => {
     const posted: { kind: string; message?: string }[] = []
     process.env.DSH_DIALOG_TITLE = 'Pick'
-    ;(process as { send?: unknown }).send = (message: { kind: string }, callback?: () => void) => {
+    // Never invoke the post callback: it runs the worker's disconnect(), and
+    // this process is IPC-connected under the forks pool — severing vitest's
+    // own channel would kill the test worker. The real close lifecycle
+    // belongs to built-worker.e2e.ts.
+    ;(process as { send?: unknown }).send = (message: { kind: string }) => {
       posted.push(message)
-      callback?.()
+      return true
     }
     return { posted }
   }