feat(cli): add agent console - live multi-agent TUI

[codeaholicguy]

Summary

• Adds agent console command: a full-screen TUI that shows all running agents in real time, lets you inspect each agent's conversation, send messages, and open agent terminals without leaving the dashboard
• Left pane lists agents with status glyph, name, type, and working summary; right pane shows the last 20 messages for the selected agent with a chat input below
• Actions (open/send) dispatch via a CLI subprocess with stdio: pipe so the TUI never yields the terminal

Test plan

• agent console renders within ~1s of launch
• j/k navigates agent list; preview updates
• o opens selected agent without unmounting the TUI
• i / m focuses chat input; Enter sends message; Esc cancels
• q exits cleanly
• Resize terminal to < 120 cols, preview hides; resize back, preview reappears
• No crash when an agent is deleted mid-session