Multi-window architecture: tray-resident daemon with N child windows

[sbaker]

Summary

Evolve from a single-window Electron app to a tray-resident daemon that spawns N independent child windows. Each window owns its own workspace while the main process coordinates shared state and services.

What already works

• Tray app runs independently
• Services are window-agnostic
• Popup chat proves multi-BrowserWindow works
• Zustand stores are per-renderer

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Sub-tasks

• Create Window Manager module (Map<id, BrowserWindow>)
• Track workspace-to-window mapping
• Audit all mainWindow.webContents.send() calls (~50 occurrences)
• Replace with event.sender.send() or windowManager routing
• Track executionId to windowId mapping
• Implement broadcast for deployment/trigger state changes
• Change single instance lock to spawn new window instead of blocking
• Pass CLI args from second launch to new window
• Dynamic tray menu with window list
• Per-window file watchers
• App stays alive when all windows close (tray-only mode)
• Shared state coordination: main process registry for cross-window awareness