fix(tui): release the branch watch if the label paint throws

Clear the in-flight guard before onBranch. A throw from the paint
callback used to skip the release and the armed follow-up, so later
refreshes never looked the branch up again.

Author: TheGreatAxios

src/tui/workspace-watch.test.ts

@@ -53,6 +53,53 @@ describe("watchGitBranch", () => {
     watch.stop();
   });
 
+  test("a throwing onBranch does not stick the guard, so a later refresh looks up again", async () => {
+    let calls = 0;
+    const pending: ((branch: string | null) => void)[] = [];
+    const watch = watchGitBranch({
+      cwd: "/repo",
+      onBranch: () => {
+        throw new Error("paint failed");
+      },
+      fetchBranch: () => {
+        calls += 1;
+        return new Promise((resolve) => {
+          pending.push(resolve);
+        });
+      },
+    });
+    pending[0]?.("main");
+    await flush();
+    expect(calls).toBe(1);
+
+    watch.refresh();
+    expect(calls).toBe(2);
+    watch.stop();
+  });
+
+  test("a follow-up armed before onBranch throws still runs", async () => {
+    let calls = 0;
+    const pending: ((branch: string | null) => void)[] = [];
+    const watch = watchGitBranch({
+      cwd: "/repo",
+      onBranch: () => {
+        throw new Error("paint failed");
+      },
+      fetchBranch: () => {
+        calls += 1;
+        return new Promise((resolve) => {
+          pending.push(resolve);
+        });
+      },
+    });
+    watch.refresh();
+    expect(calls).toBe(1);
+    pending[0]?.("main");
+    await flush();
+    expect(calls).toBe(2);
+    watch.stop();
+  });
+
   test("a null result after a known branch is not reported", async () => {
     const seen: (string | null)[] = [];
     let branch: string | null = "main";

src/tui/workspace-watch.ts

@@ -50,14 +50,22 @@ export function watchGitBranch(input: BranchWatchInput): BranchWatch {
     again = false;
     fetchBranch(input.cwd).then(
       (branch) => {
-        // Null after a real branch is a failed lookup (or detached HEAD, which
-        // shares that null). Keep the suffix; do not clear it.
-        if (!stopped && !(branch === null && shown !== null)) {
-          shown = branch;
-          input.onBranch(branch);
-        }
+        // Release before paint. A throw from onBranch must not stick the
+        // guard or skip a follow-up armed while this lookup was in flight,
+        // and it must not reject this chain.
         inFlight = false;
-        if (!stopped && again) refresh();
+        try {
+          // Null after a real branch is a failed lookup (or detached HEAD,
+          // which shares that null). Keep the suffix; do not clear it.
+          if (!stopped && !(branch === null && shown !== null)) {
+            input.onBranch(branch);
+            shown = branch;
+          }
+        } catch {
+          // The label paint must not stick the lookup or reject this chain.
+        } finally {
+          if (!stopped && again) refresh();
+        }
       },
       () => {
         inFlight = false;