[joonhoekim]

Problem

Two ways rift loses track of an app, both silently.

1. A quit app is never dropped. By the time kEventAppTerminated arrives,
   GetProcessPID no longer resolves the terminated process's serial number,
   so the event is dropped. The app stays in rift-cli query applications
   with its actor and AX observer: TextEdit after Quit, or any app killed with
   SIGTERM.
2. An app busy when its actor starts is never managed. init waits two
   seconds to register the app's AX notifications. If the app refuses AX
   requests for that long, the actor exits, and only activating the app
   (retry_unattached_app) reattaches it. After a rift restart, the app's
   windows in other workspaces are still where the previous rift parked them,
   off screen and out of the overview, so nothing shows them to activate. Seen
   with Chrome and Brave after a restart: missing from query applications
   for hours until activated. The failed init is inferred (logging was at the
   default level); this change logs Could not attach a running app; trying again.

Reproduce

1. Launch TextEdit and quit it. rift-cli query applications still lists it.
2. The second can't be triggered at will: restart rift while a busy Chromium
   browser has windows in a workspace that is not shown. When its actor gives
   up, the app never shows up in query applications.

Fix

• Commit 1: when a termination's pid cannot be read, each active app that
  NSRunningApplication no longer reports as running is terminated as
  AppTerminated would terminate it (WmEvent::AppsMayHaveTerminated).
• Commit 2: AppLifecycle::sync matches actors to the running apps in both
  directions: running regular apps with no actor are attached, and actors
  whose app no longer runs are terminated (the check from commit 1). It runs
  on app activation, deactivation and space state updates (at most once a
  second), and when a retry falls due: an actor that gives up while its app
  runs is retried after 2 s, doubling up to 5 min.

Testing

• New tests in wm_controller.rs (app_lifecycle_tests).
• cargo test --lib: 888 passed. The 2 failures also fail on main (fixed
  separately in test: keep the window server's Space window lists out of unit tests #640).
• cargo +nightly fmt --all --check.
• By hand on macOS 27.0.1: TextEdit and an app killed with SIGTERM drop out of
  query applications. I could not make an app refuse AX on demand, so the
  retry path itself is covered by the unit tests only.