feat(json): add interactive JSON tree viewer with collapse/expand and rainbow colors (#786)

- Add JsonTreeViewer component with collapse/expand for nested objects and arrays
- Add rainbow colors by depth level using CSS color-mix() with syntax theme tokens
- Add virtualization support (@tanstack/react-virtual) for large JSON files (>200 nodes)
- Add JsonTreeView wrapper with Expand All / Collapse All toolbar
- Integrate into FilesView: tree/text toggle button, JSON file detection
- Integrate into ToolPart: auto-detect JSON tool outputs, render as tree
- Integrate into ToolOutputDialog: JSON tree view in expanded dialog
- Add jsonTreeUtils.ts: parse, flatten, path utilities

No new dependencies - uses existing @tanstack/react-virtual.
Colors derived from existing syntax.* theme tokens - works across all themes.

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/chat/message/toolRenderers.tsx

@@ -28,6 +28,36 @@ const formatInputForDisplay = (input: Record<string, unknown>, toolName?: string
     return formatToolInput(input, toolName || '');
 };
 
+export const tryParseJsonOutput = (output: string): { data: unknown; isJson: boolean } => {
+    if (!output || typeof output !== 'string') {
+        return { data: null, isJson: false };
+    }
+
+    const trimmed = output.trim();
+
+    if (!trimmed.startsWith('{') && !trimmed.startsWith('[')) {
+        return { data: null, isJson: false };
+    }
+
+    if (!trimmed.endsWith('}') && !trimmed.endsWith(']')) {
+        return { data: null, isJson: false };
+    }
+
+    if (trimmed.length < 2) {
+        return { data: null, isJson: false };
+    }
+
+    try {
+        const parsed = JSON.parse(trimmed);
+        if (parsed !== null && typeof parsed === 'object') {
+            return { data: parsed, isJson: true };
+        }
+        return { data: null, isJson: false };
+    } catch {
+        return { data: null, isJson: false };
+    }
+};
+
 export const formatEditOutput = (output: string, toolName: string, metadata?: Record<string, unknown>): string => {
     let cleaned = cleanOutput(output);