[FEATURE]: Click MCP entries in the TUI sidebar to toggle them on/off #40521

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Problem

I have a lot of good MCPs to use, but I don't want them all taking up resources all the time.

The right-side sidebar already shows a list of MCP servers with their current status.
You can click the MCP header to expand/collapse the section, but the individual server rows are display-only.

To enable or disable an MCP you currently have to:

1. Type /mcp (or /mcps)
2. Or open the command palette → “Toggle MCPs”
3. Then use Space (or the dialog controls)

This is an extra step when the list of active MCPs is already visible right next to the conversation.

Proposed Solution

Make each MCP entry in the sidebar clickable so that clicking it toggles the server on/off for the current session (the same behavior that already exists in the /mcp dialog).

• Clicking a connected/enabled MCP → disconnects / disables it
• Clicking a disabled MCP → connects / enables it
• Visual feedback (status indicator + maybe a brief highlight) should update immediately
• The toggle should use the existing session-scoped MCP connect/disconnect logic

Why this would be useful

• Faster workflow when you only need an MCP for a short time
• Matches the “click what you see” interaction model that already works for the section headers
• The toggle logic and mouse handling already exist in the TUI; this would just wire the sidebar rows to it

Additional context

Mouse support is already enabled by default ("mouse": true in tui.json).
The sidebar MCP section is rendered in the session view and already has onMouseDown handlers on the header.