tools.workspace-manager: simplify architecture
- Daemon: only tracks workspace/directory, emits events, persists tabs
- Remove on_create/on_enter/on_leave hooks, tmux management, restore flag
- Firefox extension: saves tabs to ~/workspaces/<name>.json via daemon
- Firefox extension: anchor window keeps Firefox alive, hidden in scratchpad
- Daemon registers sway for_window rule before Firefox starts
- Firefox service: Restart=always, starts after workspace-manager
- Native host: passes tab save/load through daemon (single writer)
- Workspace menu: simplified to restore tabs, close, edit, delete
- Remove workspace-on-new.sh (no longer needed)
- NixOS module: only directory option remains