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/dashboard/src/dashboard.css

@@ -1096,6 +1096,7 @@ code {
 .rqe-source-manual { color: var(--cyan); border-color: var(--cyan); }
 .rqe-source-meta_update { color: var(--purple); border-color: var(--purple); }
 .rqe-source-auto_update { color: var(--muted); }
+.rqe-source-startup_sweep { color: var(--muted); }
 .rqe-source-crash_recover { color: var(--amber); border-color: var(--amber); }
 .rqe-source-approval { color: var(--green); border-color: var(--green); }
 .rqe-when { color: var(--muted); font-size: 0.85em; }

frontend/packages/dashboard/src/tabs.js

@@ -551,7 +551,7 @@ window.marked = marked;
     // no-op-when-target-absent convention the other renderers
     // (renderTombstones, etc.) follow.
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
 
     // Containers come from the derived map (event-driven) rather than
     // `s.containers`; `s` still supplies hostname (for the web-ui
@@ -883,7 +883,7 @@ window.marked = marked;
     // Recompute action availability + tooltips per render. Each
     // action declares which agents it CAN'T run on; the bar disables
     // the button and surfaces the offending names in the tooltip.
-    actions.innerHTML = '';
+    actions.replaceChildren();
     const allRunning = selected.every((c) => c.running);
     const allStopped = selected.every((c) => !c.running);
     const noManagers = selected.every((c) => !c.is_manager);
@@ -1114,7 +1114,7 @@ window.marked = marked;
     // no-op on /flow.html and any other page that loads the shared
     // bundle without the dashboard's tab panes.
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     if (!s.tombstones || !s.tombstones.length) {
       root.append(el('p', { class: 'empty' }, 'no kept state — clean'));
       return;
@@ -1181,21 +1181,21 @@ window.marked = marked;
   async function fetchAndRenderToolGroups() {
     const root = $('tool-groups-section');
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     root.append(el('p', { class: 'meta' }, 'loading…'));
     try {
       const resp = await fetch('/api/tool-groups');
-      if (!resp.ok) throw new Error('HTTP ' + resp.status);
+      if (!resp.ok) throw new Error('http ' + resp.status);
       const data = await resp.json();
       renderToolGroups(root, data);
     } catch (err) {
-      root.innerHTML = '';
+      root.replaceChildren();
       root.append(el('p', { class: 'meta' }, 'fetch failed: ' + err));
     }
   }
 
   function renderToolGroups(root, data) {
-    root.innerHTML = '';
+    root.replaceChildren();
     const { groups, assignments } = data;
     if (!groups || !groups.length) {
       root.append(el('p', { class: 'meta' }, '(no tool groups defined)'));
@@ -1380,7 +1380,7 @@ window.marked = marked;
     // no-op when the section is missing. `question_added` /
     // `question_resolved` SSE events route through here.
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     const fmt = (n) => new Date(n * 1000).toISOString().replace('T', ' ').slice(0, 19);
     const allPending = questionsState.pending;
     const activeFilter = getQuestionsFilter();
@@ -1712,7 +1712,7 @@ window.marked = marked;
   function renderPeerHives(peers) {
     const root = $('peers-section');
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     if (!peers || !peers.length) {
       root.append(el('p', { class: 'empty' }, 'no peer hives configured'));
       return;
@@ -1743,7 +1743,7 @@ window.marked = marked;
     // no-op elsewhere — `approval_added` / `approval_resolved` SSE
     // events route through here on every page that loads the bundle.
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
 
     // Spawn request form: submitting it queues a Spawn approval that
     // lands in this same list, so the form belongs here rather than on
@@ -1933,7 +1933,7 @@ window.marked = marked;
   function renderMetaInputs(s) {
     const root = $('meta-inputs-section');
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     const inputs = s.meta_inputs || [];
     if (!inputs.length) {
       root.append(el('p', { class: 'empty' }, 'meta repo not seeded yet'));
@@ -2054,7 +2054,7 @@ window.marked = marked;
   function renderRebuildQueue(s) {
     const root = $('rebuild-queue-section');
     if (!root) return;
-    root.innerHTML = '';
+    root.replaceChildren();
     const queue = s.rebuild_queue || [];
     if (!queue.length) {
       root.append(el('p', { class: 'empty' }, 'queue is empty — nothing pending or in flight.'));
@@ -3578,7 +3578,7 @@ window.marked = marked;
 
     // Step 4: rebuild the dropdown from the two overflow sets.
     const overflowedTabs = [...dynamicOverflow, ...defaultOverflow];
-    overflowDrop.innerHTML = '';
+    overflowDrop.replaceChildren();
     for (const tab of overflowedTabs) {
       const li = document.createElement('li');
       li.setAttribute('role', 'presentation');