fix(tui): display dynamically registered MCP servers in status

[altendky]

fixes #7482

MCP servers registered via POST /mcp were working (tools available) but
not appearing in the TUI /status dialog. This was because MCP.status()
only returned config-based servers, and the TUI didn't refresh after
dynamic registration.

Changes:

• MCP.status() now includes dynamically registered MCPs from state
• Added TuiEvent.McpRefresh event to signal MCP status changes
• MCP.add() publishes McpRefresh when a new server is added
• TUI sync context listens for McpRefresh and refetches status

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

The search results show one potentially related PR:

• PR feat: show skills in status and sidebar #6154: "feat: show skills in status and sidebar"
  feat: show skills in status and sidebar #6154

  This may be related as it involves displaying items in the TUI status and sidebar, which is similar functionality to displaying MCP servers in the status dialog. However, it appears to focus on skills rather than MCP servers specifically, so it's likely a different feature area.

All other searches returned only the current PR (#7119) itself. No other duplicate or directly related PRs addressing the same MCP server status registration issue were found.

[altendky]

as context, i was integrating the opencode vscode extension with the vscode-mcp-server. it was working but the mcp server list wasn't reporting it.