fix(levelcode-ai): tear down group + label state on reset / checkpoint restore

Review caught that the new calm-transcript state outlives a log wipe:

- The `reset` handler cleared the log HTML and the card/step maps but left
  `curGroup` pointing at the now-detached `.groupbody` and `turnLabeled` set.
  The next run would append into disconnected DOM (nothing shows), and the first
  assistant line would render as an unlabeled continuation. Reset both now.

- `applyCheckpointRestored` removes this turn's (and later turns') DOM and pruned
  only the card maps — the step maps and a possibly-stranded `curGroup` were left
  behind. It now prunes editSteps/termSteps/verifySteps too and drops the group
  if its element was removed. (This also completes the earlier request to prune
  step maps on checkpoint restore, not just on reset.)

- `pruneDetached` is now dual-mode: it follows `.card` for step-map values, so
  the same helper works for both card and step maps.

webviewCss +2 static guards. Gate green (22 suites).

Author: ndemianc

extensions/levelcode-ai/media/chat.html

@@ -2814,12 +2814,16 @@
     let wrap = u.querySelector('.ckwrap'); if (!wrap){ wrap = document.createElement('div'); wrap.className = 'ckwrap'; u.appendChild(wrap); }
     renderRestoreIdle(wrap, turnId, fileCount);
   }
-  function pruneDetached(map){ for (const k in map){ const el = map[k]; if (el && !log.contains(el)){ delete map[k]; } } }
+  // Drop entries whose DOM is gone. Works for card maps (value IS the element) and step maps (value
+  // is a {card} object) — a checkpoint restore removes the cards, so their step state must go too.
+  function pruneDetached(map){ for (const k in map){ const v = map[k]; const el = (v && v.nodeType) ? v : (v && v.card); if (!el || !log.contains(el)){ delete map[k]; } } }
   function applyCheckpointRestored(m){
     const u = ckBubble(m.turnId); if (!u){ return; }
     let n = u.nextSibling; while (n){ const next = n.nextSibling; n.remove(); n = next; }   // drop this turn's output + every later turn
     const wrap = u.querySelector('.ckwrap'); if (wrap){ wrap.innerHTML = '<span class="ckmuted">' + REVERT + ' Restored to here · ' + (m.filesRestored || 0) + ' file' + (m.filesRestored === 1 ? '' : 's') + ' reverted</span>'; }
     pruneDetached(editCards); pruneDetached(termCards); pruneDetached(verifyCards);
+    pruneDetached(editSteps); pruneDetached(termSteps); pruneDetached(verifySteps);
+    if (curGroup && !log.contains(curGroup.el)){ curGroup = null; }   // don't append into a removed group
     agentBubble = null; agentRaw = ''; setStreaming(false); forceStick();
   }
   function checkpointBusyNotice(m){
@@ -2914,6 +2918,10 @@
     else if (m.type === 'clearContext'){ selLabel = null; renderChips(); }
     else if (m.type === 'reset'){
       log.innerHTML = '<div id="empty"><div class="big">New chat</div>Ask about your code, or describe what to build.</div>';
+      // Wiping the log detaches any open group; drop the dangling refs so the next run starts clean —
+      // otherwise groupAppend() appends into a disconnected .groupbody (nothing shows), and a stale
+      // turnLabeled makes the first assistant line render as an unlabeled continuation.
+      curGroup = null; turnLabeled = false;
       selLabel = null; ctxFiles = []; renderChips();
       for (const k in editCards) { delete editCards[k]; } for (const k in termCards) { delete termCards[k]; } for (const k in verifyCards) { delete verifyCards[k]; } for (const k in bgTasks) { delete bgTasks[k]; }
       for (const k in editSteps) { delete editSteps[k]; } for (const k in termSteps) { delete termSteps[k]; } for (const k in verifySteps) { delete verifySteps[k]; }   // step maps ride with their cards

extensions/levelcode-ai/test/webviewCss.test.js

@@ -114,4 +114,21 @@ test('every check migrated to the ring-check — no bare codicon(\'check\') anyw
 		'and drops its own border so there is a single ring, not two');
 });
 
+// New calm-transcript state (curGroup, turnLabeled) must be torn down wherever the log is wiped,
+// or the next run appends into a detached group (nothing shows) and the first line renders unlabeled.
+test('the reset handler clears the group + speaker-label state, not just the card maps', () => {
+	const reset = html.slice(html.indexOf("m.type === 'reset'"), html.indexOf("m.type === 'reset'") + 900);
+	assert.ok(/curGroup = null/.test(reset), 'reset drops the open-group ref');
+	assert.ok(/turnLabeled = false/.test(reset), 'reset re-arms the speaker label');
+});
+
+test('a checkpoint restore prunes step maps and drops a group whose DOM was removed', () => {
+	const fn = html.slice(html.indexOf('function applyCheckpointRestored'), html.indexOf('function applyCheckpointRestored') + 900);
+	assert.ok(/pruneDetached\(editSteps\)/.test(fn) && /pruneDetached\(termSteps\)/.test(fn) && /pruneDetached\(verifySteps\)/.test(fn),
+		'the step maps are pruned alongside the card maps');
+	assert.ok(/curGroup && !log\.contains\(curGroup\.el\)/.test(fn), 'a stranded (detached) group is dropped');
+	// pruneDetached must handle both an element value and a {card} step value
+	assert.ok(/function pruneDetached\(map\)\{[^}]*\.card/.test(html), 'pruneDetached also follows step.card');
+});
+
 console.log('webviewCss: ' + n + ' tests passed');