refactor(coding-agent): restored static computer worker start hook

- The pi-utils/mime subpath fix made the computer worker graph lazy-safe,
  so the dynamic-import dispatch added for laziness is no longer needed;
  cli.ts and the bundled-host fixture statically import
  startComputerWorker() per the no-inline-import rule.
- worker-entry keeps the selector-guarded direct-source auto-start; the
  worker-selector test now pins the exported hook contract. Verified
  --no-addons CLI startup stays addon-free and the bundled/compiled
  worker-host tests pass.

packages/coding-agent/test/worker-selector.test.ts

@@ -38,7 +38,9 @@ describe("worker selector dispatch", () => {
 });
 
 describe("computer worker entry", () => {
-	it("is side-effect-free to import outside a worker and has no manual start hook", () => {
-		expect("startComputerWorker" in computerWorkerEntry).toBe(false);
+	it("is side-effect-free to import outside a worker and exposes a named start function", () => {
+		// Importing on the main thread (no parentPort) must not start the worker
+		// core; the CLI host and bundled hosts call the exported hook explicitly.
+		expect(computerWorkerEntry.startComputerWorker).toBeFunction();
 	});
 });