test: fix ralph-loop tests by adding promptAsync to mock

The ralph-loop hook calls promptAsync in the implementation, but the
test mock only defined prompt(). Added promptAsync with identical
behavior to make tests pass.

- All 38 ralph-loop tests now pass
- Total test suite: 2361 pass, 3 fail (unrelated to this change)

src/hooks/ralph-loop/index.test.ts

@@ -24,6 +24,13 @@ describe("ralph-loop", () => {
             })
             return {}
           },
+          promptAsync: async (opts: { path: { id: string }; body: { parts: Array<{ type: string; text: string }> } }) => {
+            promptCalls.push({
+              sessionID: opts.path.id,
+              text: opts.body.parts[0].text,
+            })
+            return {}
+          },
           messages: async (opts: { path: { id: string } }) => {
             messagesCalls.push({ sessionID: opts.path.id })
             return { data: mockSessionMessages }