React error boundaries for chat message rendering

[ryuhmanov-m]

Parent issue: #20

Context

If a single message fails to render (e.g., malformed markdown, unexpected tool output), it can crash the entire chat view. Error boundaries would contain failures to individual messages.

Scope

1. Create src/components/ui/ErrorBoundary.tsx — a reusable React error boundary component
   • Shows a friendly error message instead of crashing
   • "Retry" button to attempt re-render
   • Logs the error details to console for debugging
2. Wrap MessageBubble / MessageContent in the error boundary
3. Wrap ToolCallDisplay in the error boundary (tool results can have unexpected shapes)

Design

Error state should show something like:

"This message couldn't be displayed. [Show details] [Retry]"

Keep the styling consistent with the existing chat theme.

References

• Message components: src/components/chat/
• React docs on error boundaries: https://react.dev/reference/react/Component#catching-rendering-errors-with-an-error-boundary