Start notification-mode runs before watch discovery

[longlho]

Why

Notification-mode devservers can stay alive while iBazel discovers their watch graph. Waiting for that query before launch puts a large, unnecessary delay on startup.

What changed

Port bazelbuild/bazel-watcher#838 onto the Perplexity fork:

• start notification-mode runs before watch discovery
• install watchers afterward and send a catch-up graph build
• preserve query-first behavior for restart-mode targets, builds, tests, and coverage
• compose the upstream lifecycle change with our structured BEP output notifications