feat: context compaction button in token bar (≥50% usage)

src/App.tsx

@@ -43,6 +43,21 @@ export default function App() {
     setSplitSession(prev => prev === key ? null : key);
   }, []);
 
+  const handleCompact = useCallback(async (key: string): Promise<boolean> => {
+    const client = getClient();
+    if (!client) return false;
+    try {
+      const res = await client.send('sessions.compact', { key });
+      // Reload history after compaction to reflect new state
+      if (res?.compacted) {
+        switchSession(key);
+      }
+      return !!res?.compacted;
+    } catch {
+      return false;
+    }
+  }, [getClient, switchSession]);
+
   // Split pane drag
   useEffect(() => {
     if (!splitDragging) return;
@@ -152,7 +167,7 @@ export default function App() {
       <div ref={splitContainerRef} className="flex-1 flex min-w-0" aria-hidden={sidebarOpen ? true : undefined}>
         {/* Primary pane */}
         <main className="flex flex-col min-w-0" style={splitSession ? { width: `${splitRatio}%` } : { flex: 1 }} aria-label={t('app.mainChat')}>
-          <Header status={status} sessionKey={activeSession} onToggleSidebar={() => setSidebarOpen(!sidebarOpen)} activeSessionData={sessions.find(s => s.key === activeSession)} onLogout={logout} soundEnabled={soundEnabled} onToggleSound={toggleSound} messages={messages} agentAvatarUrl={agentIdentity?.avatar} agentName={agentIdentity?.name} />
+          <Header status={status} sessionKey={activeSession} onToggleSidebar={() => setSidebarOpen(!sidebarOpen)} activeSessionData={sessions.find(s => s.key === activeSession)} onLogout={logout} soundEnabled={soundEnabled} onToggleSound={toggleSound} messages={messages} agentAvatarUrl={agentIdentity?.avatar} agentName={agentIdentity?.name} onCompact={handleCompact} />
           <ConnectionBanner status={status} />
           <Suspense fallback={<div className="flex-1 flex items-center justify-center text-pc-text-muted"><div className="animate-pulse text-sm">Loading…</div></div>}>
             <Chat messages={messages} isGenerating={isGenerating} isLoadingHistory={isLoadingHistory} status={status} sessionKey={activeSession} onSend={sendMessage} onAbort={abort} agentAvatarUrl={agentIdentity?.avatar} />