Problem
if multi mcp is configured. Startup takes several seconds before entering tui.

Proposed change
Add a loading mark to imply that startup has not finished.
Chat is fine whiling loading. When mcp is required but still loading, just wait.

Alternatives considered
To be honest, it not that important because open/close reasionix frequently is not common.

Scope check

• This belongs in core reasonix (not better as a separate npm package)
• I've read CLAUDE.md and CONTRIBUTING.md