chore: replaceChildren + http case in flow.js and logs.js

Same cleanup as the previous pass (tabs.js, app.js): replace
innerHTML = '' with replaceChildren() and lowercase the one
uppercase 'HTTP' error in logs.js.

frontend/packages/dashboard/src/flow.js

@@ -101,7 +101,7 @@ import {
   (() => {
     const flow = $('msgflow');
     if (!flow) return;
-    flow.innerHTML = '';
+    flow.replaceChildren();
     const tsFmt = (n) => new Date(n * 1000).toISOString().slice(11, 19);
     // Pulse the page banner whenever a broker event lands. The
     // `.banner` element lives in the dashboard's <footer> rather than
@@ -286,11 +286,11 @@ import {
     }
     function hideSuggest() {
       suggest.hidden = true;
-      suggest.innerHTML = '';
+      suggest.replaceChildren();
       suggestActive = -1;
     }
     function renderSuggest(matches) {
-      suggest.innerHTML = '';
+      suggest.replaceChildren();
       if (!matches.length) { hideSuggest(); return; }
       for (let i = 0; i < matches.length; i += 1) {
         const item = document.createElement('div');

frontend/packages/dashboard/src/logs.js

@@ -60,13 +60,13 @@ import {
 
   async function fetchBuild() {
     if (!buildList) return;
-    buildList.innerHTML = '';
+    buildList.replaceChildren();
     buildList.append(el('p', { class: 'meta' }, 'loading…'));
     try {
       const resp = await fetch('/api/build-logs?limit=30');
-      if (!resp.ok) throw new Error('HTTP ' + resp.status);
+      if (!resp.ok) throw new Error('http ' + resp.status);
       const rows = await resp.json();
-      buildList.innerHTML = '';
+      buildList.replaceChildren();
       if (!rows || rows.length === 0) {
         buildList.append(el('p', { class: 'meta' }, '(no build logs yet)'));
         return;
@@ -111,7 +111,7 @@ import {
           }
           // already loaded?
           if (detail.dataset.loaded) return;
-          detail.innerHTML = '';
+          detail.replaceChildren();
           detail.append(
             el('a', {
               href: '/api/build-logs/id/' + h.id + '/raw',
@@ -176,7 +176,7 @@ import {
       }
       buildList.append(ul);
     } catch (err) {
-      buildList.innerHTML = '';
+      buildList.replaceChildren();
       buildList.append(el('p', { class: 'meta' }, 'fetch failed: ' + err));
     }
   }
@@ -197,7 +197,7 @@ import {
       if (!resp.ok) return;
       const state = await resp.json();
       if (!agentSelect) return;
-      agentSelect.innerHTML = '';
+      agentSelect.replaceChildren();
       agentSelect.append(el('option', { value: '' }, '— select agent —'));
       for (const c of (state.containers || [])) {
         agentSelect.append(el('option', { value: c.name }, c.name));