fix: drain postHookActions even with no registered handlers

Remove early return in triggerInternalHook that skipped the post-hook
drain when allHandlers was empty. This was a latent footgun: any
postHookActions pre-populated on the event before calling
triggerInternalHook would be silently dropped if no handlers were
registered for that event type.

Update test to verify post-hooks now drain in the no-handlers case.

src/hooks/internal-hooks.test.ts

@@ -529,13 +529,15 @@ describe("hooks", () => {
       expect(event.postHookActions).toEqual([]);
     });
 
-    it("does not run post-hook actions when no handlers are registered", async () => {
+    it("drains post-hook actions even when no handlers are registered", async () => {
       const event = createInternalHookEvent("command", "new", "test-session");
+      let ran = false;
       event.postHookActions.push(() => {
-        throw new Error("should not run");
+        ran = true;
       });
-      // triggerInternalHook returns early when no handlers — post-hooks don't run
-      await expect(triggerInternalHook(event)).resolves.not.toThrow();
+      // No handlers registered — post-hooks should still drain
+      await triggerInternalHook(event);
+      expect(ran).toBe(true);
     });
   });
 

src/hooks/internal-hooks.ts

@@ -279,10 +279,6 @@ export async function triggerInternalHook(event: InternalHookEvent): Promise<voi
 
   const allHandlers = [...typeHandlers, ...specificHandlers];
 
-  if (allHandlers.length === 0) {
-    return;
-  }
-
   for (const handler of allHandlers) {
     try {
       await handler(event);