Add TUI console toggler for MCP servers

Update after rebasing against current master (v0.41): some MCP plumbing and display work has now landed upstream, so the original description overstated what remains in my branch.

Current state on master

Master already has:

• MCP management tool actions: list, connect, disconnect, reload
• MCP config loading/reload support
• MCP server state plumbing through TUI state
• MCP server display in the header/status area

Master does not yet have:

• A /mcp slash command
• An inline TUI picker/switcher for MCP servers
• Space-to-toggle enable/disable UX
• A clear runtime policy for hiding disabled server tools from model prompts/tool schemas

Current state of my branch

Reference branch: https://github.com/alecuba16/jcode/tree/feature/mcp-server-toggles

Latest branch head: c4e68c36

Compare: https://github.com/1jehuang/jcode/compare/master...alecuba16:jcode:feature/mcp-server-toggles

After rebasing on current master, the branch now includes:

• Overview widget: Shows enabled MCP servers with tool counts in the fixed Overview panel
• Enable/disable toggle: enable and disable actions on the mcp tool that persist to ~/.jcode/mcp.json
  • Disabling a server disconnects it and unregisters its tools from the prompt
  • Enabling a server connects it and registers its tools into the prompt
• Matches opencode behavior for toggling MCP servers on/off

Files changed: crates/jcode-app-core/src/tool/mcp.rs, crates/jcode-tui/src/tui/app/tui_state.rs, crates/jcode-tui/src/tui/info_widget.rs, crates/jcode-tui/src/tui/info_widget_tests.rs

The branch ahead by 1, behind by 0 relative to upstream master (rebased on latest).

Requested follow-up

Add a TUI console MCP switcher so users can enable/disable configured MCP servers without editing config files or restarting.

Suggested UX:

• /mcp opens an inline picker listing configured MCP servers
• Space toggles a server enabled/disabled for the current session
• Enter applies changes
• Disabled servers should not expose their MCP tools to the model prompt/tool schema
• UI should show enough status to understand which servers are enabled, disabled, connected, or unavailable

Design decisions needed

• Should toggles be session-only, persisted to config, or support both?
• If a connected server is disabled, should it disconnect immediately or only hide its tools?
• How should global vs project MCP config precedence interact with per-session toggles?
• How should remote sessions receive and apply the enabled/disabled server list?

Acceptance criteria

• Users can open a TUI MCP switcher from the console
• Users can toggle configured MCP servers without editing JSON manually
• Disabled server tools are omitted from model-visible tools at runtime
• Current MCP management actions (list, connect, disconnect, reload) continue to work
• Header/info-widget MCP status remains accurate after toggles
• Tests cover picker rendering, toggle behavior, and disabled-tools filtering

Start by reading crates/jcode-app-core/src/tool/mcp.rs and crates/jcode-tui/src/tui/app/tui_state.rs, then inspect crates/jcode-tui/src/tui/info_widget.rs and crates/jcode-tui/src/tui/info_widget_tests.rs. Done means the TUI provides the requested picker and toggle behavior, disabled tools are filtered, status remains accurate, existing MCP actions continue to work, and tests cover rendering and behavior.