feat(hooks): use auto flag for session resumption after compaction

- executor.ts: Added `auto: true` to summarize body, removed subsequent prompt_async call
- preemptive-compaction/index.ts: Added `auto: true` to summarize body, removed subsequent promptAsync call
- executor.test.ts: Updated test expectation to include `auto: true`

Instead of sending 'Continue' prompt after compaction, use SessionCompaction's `auto: true` feature which auto-resumes the session.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/hooks/anthropic-context-window-limit-recovery/executor.test.ts

@@ -257,7 +257,7 @@ describe("executeCompact lock management", () => {
     expect(mockClient.session.summarize).toHaveBeenCalledWith(
       expect.objectContaining({
         path: { id: sessionID },
-        body: { providerID: "anthropic", modelID: "claude-opus-4-5" },
+        body: { providerID: "anthropic", modelID: "claude-opus-4-5", auto: true },
       }),
     )