fix(v0.21): harden /track refresh and finalization lifecycle

src/app/TerminalApp.ts

@@ -8694,6 +8694,9 @@ export class TerminalApp {
     if (block && watch.status === 'stopped' && !block.finalized) {
       block.finalized = true;
       this.output.addFrontendBlock(`/track ${watch.command}`, finalResultRows(watch));
+      // The anchored transcript row can render its stopped state directly from the task.
+      // The mutable per-tracker height bookkeeping is no longer needed after finalization.
+      this.trackBlocks.delete(watch.id);
     }
     this.render();
   });

src/tasks/WatchTasks.ts

@@ -205,6 +205,9 @@ export class WatchTasks {
       return true;
     }
     this.children.set(id, child);
+    // Notify the presenter when a refresh begins, not only when it completes:
+    // a slow sample must be shown as refreshing while its previous result stays visible.
+    this.emit(watch);
     const take = (decoder: StringDecoder, chunk: Buffer) => {
       const kept = Math.min(chunk.length, Math.max(0, MAX_OUTPUT - receivedBytes));
       if (kept) { receivedBytes += kept; output += decoder.write(chunk.subarray(0, kept)); }

tests/track.test.ts

@@ -103,6 +103,27 @@ test('/track reuses one current and previous snapshot, does not overlap manual r
   }
 });
 
+test('/track emits a live refresh-start event before the sample completes', async () => {
+  const cwd = mkdtempSync(join(tmpdir(), 'nmsh-track-refresh-'));
+  const engine = new WatchTasks('/bin/sh');
+  try {
+    const task = engine.start('sleep 0.2; printf "ready\\n"', cwd, 5000,
+      {kind: 'allowed', network: false, remote: false});
+    await waitFor(() => task.runs === 1);
+    let notifiedWhileSampling = false;
+    const unsubscribe = engine.onChange(changed => {
+      if (changed.id === task.id && engine.sampling(task.id)) notifiedWhileSampling = true;
+    });
+    assert.equal(engine.runNow(task.id), true);
+    assert.equal(notifiedWhileSampling, true, 'presenter is notified during refresh');
+    await waitFor(() => task.runs === 2);
+    unsubscribe();
+  } finally {
+    engine.dispose();
+    rmSync(cwd, {recursive: true, force: true});
+  }
+});
+
 test('/track strips terminal control sequences from the displayed snapshot', async () => {
   const cwd = mkdtempSync(join(tmpdir(), 'nmsh-track-controls-'));
   const engine = new WatchTasks('/bin/sh');

tests/trackApp.test.ts

@@ -45,6 +45,7 @@ test('/track in the app: one block whose live result refreshes in place; /track
     const text = stored(app).join('\n');
     assert.match(text, /Stopped · last result \d\d:\d\d:\d\d · exit 0 · \d+ runs?\n\s*two/u);
     assert.equal(text.split('Stopped · last result').length, 2, 'written once');
+    assert.equal(app['trackBlocks'].size, 0, 'a stopped tracker releases its live height bookkeeping');
     assert.match(live(app)[0] ?? '', /^■ stopped/u, 'the live rows end with the stopped state');
 
     app['handleWatch']('/watch ls', 'start', 'ls', false);