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/components/ToolCall.tsx

@@ -1,8 +1,9 @@
-import { useState, useCallback, useMemo } from 'react';
+import { useState, useCallback, useMemo, useEffect, useRef } from 'react';
 import { ChevronRight, ChevronDown, Check, Copy } from 'lucide-react';
 import hljs from 'highlight.js/lib/common';
 import { useT } from '../hooks/useLocale';
 import { ImageBlock } from './ImageBlock';
+import { useToolCollapse } from '../contexts/ToolCollapseContext';
 
 type ToolColor = { border: string; bg: string; text: string; icon: string; glow: string; expandBorder: string; expandBg: string };
 
@@ -217,8 +218,19 @@ function extractImageFromResult(result: string): { src: string; remaining: strin
 export function ToolCall({ name, input, result }: { name: string; input?: Record<string, unknown>; result?: string }) {
   const t = useT();
   const [open, setOpen] = useState(false);
+  const { globalState, version } = useToolCollapse();
+  const lastVersion = useRef(version);
   const c = getColor(name);
 
+  // Respond to global collapse/expand commands
+  useEffect(() => {
+    if (version !== lastVersion.current) {
+      lastVersion.current = version;
+      if (globalState === 'collapse-all') setOpen(false);
+      else if (globalState === 'expand-all') setOpen(true);
+    }
+  }, [globalState, version]);
+
   const inputStr = input ? (typeof input === 'string' ? input : JSON.stringify(input, null, 2)) : '';
   const hint = getContextHint(name, input);