build-logs viewer: add --crust var + aria-expanded on row buttons (argus nits)

frontend/packages/dashboard/src/dashboard.css

@@ -487,7 +487,7 @@ a:hover {
 .journal-refresh { font-size: 0.75em; padding: 0.15em 0.5em; }
 .journal-output {
   margin: 0;
-  background: #11111b;
+  background: var(--crust);
   color: var(--fg);
   border: 1px solid var(--purple-dim);
   padding: 0.5em 0.7em;
@@ -572,7 +572,7 @@ a:hover {
 .build-logs-detail { padding: 0 0.4em 0.4em; }
 .build-logs-output {
   margin: 0;
-  background: #11111b;
+  background: var(--crust);
   color: var(--fg);
   border: 1px solid var(--purple-dim);
   padding: 0.5em 0.7em;

frontend/packages/dashboard/src/tabs.js

@@ -1126,7 +1126,7 @@ window.marked = marked;
             const age = h.started_at
               ? fmtAgeSecs(nowUnix - h.started_at) + ' ago' : '?';
             const rowBtn = el('button',
-              { type: 'button', class: 'build-logs-row-btn' },
+              { type: 'button', class: 'build-logs-row-btn', 'aria-expanded': 'false' },
               el('span', { class: `badge ${statusCls}` }, statusLabel),
               el('span', { class: 'build-logs-kind' }, h.kind),
               el('span', { class: 'build-logs-age meta' }, age),
@@ -1136,10 +1136,15 @@ window.marked = marked;
             detail.hidden = true;
             let loaded = false;
             rowBtn.addEventListener('click', async () => {
-              if (!detail.hidden) { detail.hidden = true; return; }
+              if (!detail.hidden) {
+                detail.hidden = true;
+                rowBtn.setAttribute('aria-expanded', 'false');
+                return;
+              }
               if (!loaded) {
                 detail.textContent = 'fetching…';
                 detail.hidden = false;
+                rowBtn.setAttribute('aria-expanded', 'true');
                 try {
                   const r2 = await fetch('/api/build-logs/id/' + h.id);
                   if (!r2.ok) {
@@ -1156,6 +1161,7 @@ window.marked = marked;
                 }
               } else {
                 detail.hidden = false;
+                rowBtn.setAttribute('aria-expanded', 'true');
               }
             });
             li.append(rowBtn, detail);

frontend/packages/shared/src/base.css

@@ -5,6 +5,7 @@
 :root {
   --bg: #1e1e2e;        /* base */
   --bg-elev: #181825;   /* mantle */
+  --crust: #11111b;     /* crust — terminal background */
   --fg: #cdd6f4;        /* text */
   --muted: #7f849c;     /* overlay1 */
   --purple: #cba6f7;    /* mauve */