feat: add follow option to app rules for auto workspace switching

[qeude]

Summary

Adds a follow option to app_rules that, when true, automatically switches the user to the assigned workspace when a matching window opens and the app is frontmost.

Problem

Before this change, if you had an app rule like:

{ app_id = "com.apple.dt.Xcode", workspace = 0 }

and opened Xcode while on workspace 2, the window would be created on workspace 0 but you'd stay on workspace 2. You had to manually switch to see it.

Solution

Add a follow boolean field to AppWorkspaceRule:

{ app_id = "com.apple.dt.Xcode", workspace = 0, follow = true }

When follow = true and the app is frontmost on open, the reactor triggers the existing handle_app_activation_workspace_switch path to switch to the target workspace.

Changes

• Config: add follow field to AppWorkspaceRule
• Model: propagate follow through AppRuleAssignment
• Actor/Reactor:
  • handle_application_launched: switch workspace when app opens frontmost and rule has follow = true
  • handle_window_created: switch workspace when new window opens and app is frontmost with follow = true
  • process_windows_for_app_rules: returns whether a follow is needed
  • emit_layout_events / on_windows_discovered_with_app_info: propagate follow flag
• Tests: add unit tests for model-level follow propagation, reactor-level follow detection, and the actual workspace switch mechanism
• Docs: update rift.default.toml with the new option and an example