Add cmux as the highest-priority notification provider on macOS.
cmux delivers notifications via native UNUserNotificationCenter,
properly attributed to the cmux app instead of Script Editor.
Notification priority: cmux > terminal-notifier > osascript
Tests cover the full fallback chain:
- cmux available: uses cmux, skips others
- cmux fails: falls back to terminal-notifier
- cmux + terminal-notifier fail: falls back to osascript
- cmux not available: skips to terminal-notifier
Fixes#3628
Use namespace import pattern (import * as sender) to prevent cross-file
spy leakage in Bun's shared module state. Move restoreAllMocks to
beforeEach for proper cleanup ordering.
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mrosnerr