fix(server): unlink_pull_request reports a dismissed stack PR as not linked

apps/server/src/mcp/toolkits/pullRequests/handlers.test.ts

@@ -517,6 +517,20 @@ describe("pull request toolkit handlers", () => {
     }),
   );
 
+  it.effect("reports a dismissed stack member as not linked and leaves it dismissed", () =>
+    Effect.gen(function* () {
+      const harness = yield* makeHarness({
+        thread: makeThread([makeLink(9, { source: "stack-dismissed" })]),
+      });
+      const result = yield* harness.call("unlink_pull_request", {
+        repository: "t3tools/t3code",
+        number: 9,
+      });
+      expect(result.wasLinked).toBe(false);
+      expect(yield* Ref.get(harness.commands)).toEqual([]);
+    }),
+  );
+
   it.effect("links several pull requests in one call", () =>
     Effect.gen(function* () {
       const harness = yield* makeHarness({

apps/server/src/mcp/toolkits/pullRequests/handlers.ts

@@ -446,7 +446,11 @@ const make = Effect.gen(function* () {
         const thread = yield* requireThread(PullRequestUnlinkFailedError, input.threadId);
         const project = yield* projectOf(thread, PullRequestUnlinkFailedError);
         const target = yield* resolveTarget(input, project);
-        if (!threadPullRequestsOf(thread).some((link) => threadPullRequestKeysEqual(link, target)))
+        if (
+          !threadPullRequestsOf(thread).some(
+            (link) => link.source !== "stack-dismissed" && threadPullRequestKeysEqual(link, target),
+          )
+        )
           return {
             host: target.host,
             repository: target.repository,