postrun: tighten unsubmitted-review gate to require create_pull_request_review for Review mode (#724)

The gate at `getUnsubmittedReview` accepted `toolState.finalSummaryWritten`
as a valid Review exit, contradicting the post-failure error message which
already says Review's only valid exit is `create_pull_request_review`.
This let any caller that flipped `finalSummaryWritten` — including a
`task`-dispatched `reviewfrog` subagent calling `pullfrog_report_progress`
in violation of its prose-only read-only contract — silence the gate even
when the orchestrator never submitted a review.

Split per-mode: Review requires `toolState.review`, IncrementalReview keeps
the existing `||` (its post-failure message explicitly accepts
`report_progress` as a "no review warranted" exit). Test split mirrors the
new semantics.

closes #648

agents/postRun.test.ts

@@ -29,9 +29,22 @@ describe("getUnsubmittedReview", () => {
     ).toBeNull();
   });
 
-  it("returns null when report_progress wrote a final summary", () => {
+  it("fires for Review even when report_progress wrote a final summary", () => {
+    // Review's only valid exit is `create_pull_request_review`. a summary
+    // comment is not a substitute, and accepting it here previously let
+    // subagent-flipped `finalSummaryWritten` silence the gate.
     expect(
       getUnsubmittedReview(makeToolState({ selectedMode: "Review", finalSummaryWritten: true }))
+    ).toBe("Review");
+  });
+
+  it("returns null for IncrementalReview when report_progress wrote a final summary", () => {
+    // IncrementalReview treats `report_progress` as a legitimate
+    // "no review warranted" exit, matching the post-failure error message.
+    expect(
+      getUnsubmittedReview(
+        makeToolState({ selectedMode: "IncrementalReview", finalSummaryWritten: true })
+      )
     ).toBeNull();
   });