[codex] Add running app menu

[Abdo-codes]

Summary

• Add an Add Running App submenu that lists current regular macOS apps, disables already-watched apps, and supports refresh.
• Add running-app discovery to AppLifecycleClient and reducer refresh state.
• Split MenuContentView into smaller SharedUI menu sections/utilities.
• Update README and CHANGELOG for the new workflow.

Tests

• xcodegen
• git diff --cached --check
• xcodebuild test -project Nightcap.xcodeproj -scheme Nightcap -destination 'platform=macOS,arch=arm64' -skipMacroValidation CODE_SIGNING_ALLOWED=NO -resultBundlePath TestResults.xcresult