Cleaner agent switching ux in the TUI

[krissetto]

Give it a try and let me know if this is worth a cleanup pass

⚠️ Ignore the code for now, plenty of vibes and it has not been thoroughly looked into.

• Makes the sidebar agents section its own component (as an example for future refactoring of all sections)
• Cleans up agent view in the sidebar to only show essential agent info (name and model)
• Allows switching by clicking on the agent in the sidebar
• Adds proper agent selection dialog with more info per agent and easier to read descriptions, including expandable toolset/tool list

Screencast

Screencast.From.2026-02-01.21-54-38.mp4

[krissetto]

/review

[github-actions]

Code Review Summary

Found 1 high-severity issue in the new toolset unwrapping logic that could cause a nil pointer panic.

Issues Found

• HIGH: Nil pointer dereference risk in getToolsetDisplayName function

What Looks Good

• Context cancellation properly handled in background goroutine
• Mutex protection correctly implemented for cache access
• Click handling and bounds checking are solid
• Agent picker dialog implementation looks safe