Electron App: Launch integration

[jongio]

Overview

Terminal launch integration supporting all four modes (in-place, tab, window, split pane) with shell detection and multi-session launch.

Acceptance Criteria

• Four launch modes: in-place (Enter), new tab (t), new window (w), split pane (e)
• Shell detection: discover installed shells (PowerShell, bash, zsh, fish, cmd, etc.)
• Shell picker modal when multiple shells available
• Multi-session launch: select multiple sessions then launch all (L key)
• Launch with options: yolo mode, agent override, model override, custom command
• Windows: Windows Terminal integration (wt.exe) for tab/window/pane modes
• macOS: Terminal.app / iTerm2 / Alacritty / Warp integration
• Linux: common terminal emulator detection and launch
• Launch command construction: \gh copilot session resume {id}\ with flags
• Resume interrupted sessions (R key): detect interrupted status, offer resume
• Error handling: shell not found, terminal not available, permission denied

Implementation Notes

• Launch commands executed via Node.js child_process.spawn
• Terminal detection via platform-specific logic (same as Go platform package)
• Windows Terminal pane direction: horizontal/vertical per settings
• Shell path resolution: which/where + known install locations