chore: frontend cleanup — replaceChildren, missing source badge, http case

- Replace innerHTML = '' with replaceChildren() throughout tabs.js and
  app.js (12 + 7 sites). paintAtomic already used replaceChildren; now
  the direct-clear sites are consistent with it.
- Add missing .rqe-source-startup_sweep CSS rule (startup_sweep is a
  valid QueueSource variant but had no badge style, falling through to
  the base muted appearance with no explicit intent).
- Lowercase the one uppercase 'HTTP ' in the fetchAndRenderToolGroups
  error path to match every other fetch error in the file.

frontend/packages/agent/src/app.js

@@ -549,7 +549,7 @@ window.marked = marked;
     const slot = $('term-input');
     if (!slot) return;
     if (!termInputRendered) {
-      slot.innerHTML = '';
+      slot.replaceChildren();
       const form = el('form', {
         action: 'send', method: 'POST',
         class: 'sendform-term', 'data-async': '',
@@ -790,7 +790,7 @@ window.marked = marked;
       if (slot._boundId) {
         const stillPending = pending.some((q) => q.id === slot._boundId);
         if (!stillPending && !slot._resolvedShown) {
-          slot.innerHTML = '';
+          slot.replaceChildren();
           slot.appendChild(el('span', { class: 'ask-resolved-tag' }, '[resolved]'));
           slot._resolvedShown = true;
         }
@@ -800,7 +800,7 @@ window.marked = marked;
       if (!q) continue;
       claimed.add(q.id);
       slot._boundId = q.id;
-      slot.innerHTML = '';
+      slot.replaceChildren();
       slot.appendChild(buildAnswerForm(q.id));
     }
   }
@@ -1110,7 +1110,7 @@ window.marked = marked;
         (s.status === 'needs_login_in_progress' && outLen !== lastOutputLen);
       if (dirty) {
         const root = $('status');
-        root.innerHTML = '';
+        root.replaceChildren();
         if (s.status === 'online') renderOnline(s.label, root);
         else if (s.status === 'needs_login_idle') renderNeedsLoginIdle(root);
         else if (s.status === 'needs_login_in_progress') renderLoginInProgress(s.session || {}, root);
@@ -1139,7 +1139,7 @@ window.marked = marked;
   (function() {
     const log = $('live');
     if (!log || !window.HiveTerminal) return;
-    log.innerHTML = '';
+    log.replaceChildren();
 
     function trim(s, n) { return s.length > n ? s.slice(0, n) + '…' : s; }
     // Render a message body as markdown into a new <div class="md">.
@@ -1543,7 +1543,7 @@ window.marked = marked;
             // login UI; clear it so the operator sees a clean
             // online state without a separate refetch.
             const root = $('status');
-            if (root) root.innerHTML = '';
+            if (root) root.replaceChildren();
             lastStatus = 'online';
           }
         },
@@ -1566,7 +1566,7 @@ window.marked = marked;
     // Expose the panel API for slash commands (`/help`, `/clear`).
     termAPI = {
       row: (cls, text) => term.row(cls, text),
-      clear: () => { log.innerHTML = ''; },
+      clear: () => { log.replaceChildren(); },
     };
   })();