feat(tui,dashboard,docs): add context command parity and context health panel

src/frontends/tui/components/App.tsx

@@ -12,6 +12,7 @@ import type { HookEngine, HookResult } from '../../../hooks/index.js';
 import type { ModelConfig, ModelProvider } from '../../../config/schema.js';
 import { MODEL_PROVIDERS } from '../../../config/schema.js';
 import { createClientFromConfig } from '../../../daemon/index.js';
+import { estimateMessageTokens, getContextWindow } from '../../../context/tokens.js';
 
 /** Format a tool name like "gmail.list" -> "Gmail: List" */
 function formatToolName(name: string): string {
@@ -239,6 +240,29 @@ export function App({
         return;
       }
 
+      case 'context': {
+        const history = session.getHistory();
+        const estimated = estimateMessageTokens(history);
+        const tier = modelRouter?.getTier() ?? 'default';
+        const modelName = modelRouter?.getLabel(tier) ?? model;
+        const window = getContextWindow(modelName);
+        const usagePct = window > 0 ? (estimated / window) * 100 : 0;
+        const thresholdPct = 80;
+        const thresholdTokens = Math.floor((thresholdPct / 100) * window);
+        const remaining = Math.max(0, window - estimated);
+        const text = [
+          'Context Usage (estimated)',
+          '',
+          `Model: ${modelName}`,
+          `Used: ${estimated.toLocaleString()} / ${window.toLocaleString()} tokens (${usagePct.toFixed(1)}%)`,
+          `Remaining: ${remaining.toLocaleString()} tokens`,
+          `Compaction threshold: ${thresholdPct}% (${thresholdTokens.toLocaleString()} tokens)`,
+          `Should compact: ${estimated > thresholdTokens ? 'yes' : 'no'}`,
+        ].join('\n');
+        setMessages(prev => [...prev, session.addMessage({ role: 'assistant', content: text })]);
+        return;
+      }
+
       case 'verbose': {
         const next = !verbose;
         setVerbose(next);