feat(dashboard): add GPU/VRAM usage to status channel server section

Show NVIDIA GPU utilization and VRAM used/total in the 서버 status block,
matching the existing CPU/Memory/Disk bar format. Gracefully omitted when
nvidia-smi is unavailable.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/unified-dashboard.ts

@@ -617,6 +617,39 @@ async function buildUsageContent(): Promise<string> {
     /* ignore */
   }
 
+  // GPU (optional — only shown when an NVIDIA GPU + nvidia-smi is present).
+  let gpuLine: string | null = null;
+  let vramLine: string | null = null;
+  try {
+    const out = execSync(
+      'nvidia-smi --query-gpu=utilization.gpu,memory.used,memory.total --format=csv,noheader,nounits',
+      { encoding: 'utf-8', timeout: 5000 },
+    ).trim();
+    const first = out.split('\n')[0]?.trim();
+    if (first) {
+      const [utilStr, usedStr, totalStr] = first
+        .split(',')
+        .map((s) => s.trim());
+      const gpuPct = parseInt(utilStr, 10);
+      const vramUsed = parseInt(usedStr, 10);
+      const vramTotal = parseInt(totalStr, 10);
+      if (
+        Number.isFinite(gpuPct) &&
+        Number.isFinite(vramUsed) &&
+        Number.isFinite(vramTotal) &&
+        vramTotal > 0
+      ) {
+        const vramPct = Math.round((vramUsed / vramTotal) * 100);
+        const vramUsedGB = (vramUsed / 1024).toFixed(1);
+        const vramTotalGB = (vramTotal / 1024).toFixed(1);
+        gpuLine = `${'GPU'.padEnd(8)}${bar(gpuPct)} ${String(gpuPct).padStart(3)}%`;
+        vramLine = `${'VRAM'.padEnd(8)}${bar(vramPct)} ${String(vramPct).padStart(3)}%  ${vramUsedGB}/${vramTotalGB}GB`;
+      }
+    }
+  } catch {
+    /* no GPU or nvidia-smi unavailable */
+  }
+
   lines.push('```');
   lines.push(`${'CPU'.padEnd(8)}${bar(cpuPct)} ${String(cpuPct).padStart(3)}%`);
   lines.push(
@@ -625,6 +658,8 @@ async function buildUsageContent(): Promise<string> {
   lines.push(
     `${'Disk'.padEnd(8)}${bar(diskPct)} ${String(diskPct).padStart(3)}%  ${diskUsedGB}/${diskTotalGB}GB`,
   );
+  if (gpuLine) lines.push(gpuLine);
+  if (vramLine) lines.push(vramLine);
   lines.push(`${'Uptime'.padEnd(8)}${formatElapsed(os.uptime() * 1000)}`);
   lines.push('```');