Lazy-load MCP server connections after chat window is ready

Currently, new Claude Code chat windows block until all configured MCP servers have connected (or timed out). For users with many MCP servers, this results in 1+ minute startup times before the window is usable.

Request: Initialize MCP servers lazily after the chat window opens and is ready for input. The window should be immediately usable, with MCP tools becoming available as each server connects in the background. A status indicator (e.g., a spinner or "MCP connecting..." notice) could show which servers are still loading.

Impact: Users with 5+ MCP servers experience significant startup delays. Lazy loading would make the window immediately responsive while servers connect in the background.