[FEATURE] Implement AI side-panel UI

[mikejmorgan-ai]

Description

The AI side-panel is configured in Lua but the actual UI implementation is missing.

Current State

• cx.lua has keybinding for Ctrl+Space AI panel toggle
• cx fix-last-error and cx explain commands are defined
• No actual panel rendering code exists

Required Implementation

1. Create AI panel component in wezterm-gui/src/
2. Implement panel toggle action
3. Connect to AI providers (Claude/OpenAI/Ollama)
4. Display AI responses in panel
5. Handle streaming responses

Config Reference

-- cx.lua line 244
{ key = "Space", mods = "CTRL", action = cx.action.ShowLauncherArgs { flags = "COMMANDS" } },
{ key = "f", mods = "CTRL|SHIFT", action = cx.action.SendString("cx fix-last-error\n") },
{ key = "e", mods = "CTRL|SHIFT", action = cx.action.SendString("cx explain\n") },

Estimated Time

8+ hours