feat: add collapse/expand all tool calls toggle button

Adds a floating button in the chat area that lets users collapse or expand
all tool call details at once. Useful for long conversations with many tool
calls where scrolling through expanded results is tedious.

- New ToolCollapseContext provides global collapse/expand state
- ToolCall components react to global state changes via version tracking
- Toggle button appears only when conversation has tool calls
- Supports EN/FR i18n

src/App.tsx

@@ -6,6 +6,7 @@ import { Sidebar } from './components/Sidebar';
 import { LoginScreen } from './components/LoginScreen';
 import { ConnectionBanner } from './components/ConnectionBanner';
 import { KeyboardShortcuts } from './components/KeyboardShortcuts';
+import { ToolCollapseProvider } from './contexts/ToolCollapseContext';
 
 const Chat = lazy(() => import('./components/Chat').then(m => ({ default: m.Chat })));
 
@@ -85,6 +86,7 @@ export default function App() {
   }
 
   return (
+    <ToolCollapseProvider>
     <div className="h-dvh flex overflow-x-hidden bg-[#1e1e24] text-zinc-300 bg-[radial-gradient(ellipse_at_top,rgba(255,255,255,0.02),transparent_50%),radial_gradient(ellipse_at_bottom_right,rgba(99,102,241,0.04),transparent_50%)]" role="application" aria-label="PinchChat">
       <Sidebar
         sessions={sessions}
@@ -103,5 +105,6 @@ export default function App() {
       </div>
       <KeyboardShortcuts open={shortcutsOpen} onClose={() => setShortcutsOpen(false)} />
     </div>
+    </ToolCollapseProvider>
   );
 }