[FEATURE]: Per-status MCP counts in the sidebar heading #53260

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

The session sidebar's MCP heading summarizes the servers only while the list is collapsed, and it summarizes them as two buckets:

▶ MCP (3 active, 2 errors)

"errors" lumps together failed, needs_auth and needs_client_registration, so a server that only needs an OAuth login looks the same as one that crashed. Disabled servers are not counted at all. Once the list is expanded, the heading shows nothing, so with many servers you have to scan every line to tell whether anything is wrong.

Proposal: a tui.json option, sidebar.mcp_summary:

• "default" (or unset): today's (N active, M errors) while collapsed. Nothing changes for existing users.
• "collapsed": while collapsed, show one colored status dot and count per status instead, e.g. ▶ MCP •3 •1 •1 •1.
• "always": show those per-status counts whether the list is collapsed or expanded.
• "never": show no summary.

The dots reuse the colors of the per-server dots below the heading: connected uses the success color, failed and needs client ID use the error color, needs auth uses the warning color, and disabled is muted. A status with no servers is omitted.