TUI: add an Agent Inspector modal (configured + live agent details)

[aheritier]

Problem

There is no way to inspect a single agent's full configuration or live state from the TUI — the sidebar necessarily shows only a summary.

Proposed solution

A read-only Agent Inspector modal:

• Opened by right-click on any agent (or Ctrl+click as a fallback); plain left-click switches agent.
• Title in the agent's accent color.
• Configuration: model, fallback, thinking (gauge + value), sub-agents, handoffs, skills, limits, options/flags, toolsets with their declared tools, commands.
• Live state: a current-agent marker and per-toolset status (started / stopped / error) with live tool names when a toolset is started.
• Reads only — no mutation; side-effect-free (does not start toolsets).

Scope

New dialog, mouse-gesture routing, and retaining the raw per-agent config on the team plus per-agent toolset-status/config accessors to source the data. Known limitations: skills auto-discovered from a source directory aren't enumerated; with code_mode_tools the wrapped toolset is shown.