Fix menu-bar panel presentation for accessory app

[acgxv]

Summary

• keep direct activation only on explicit panel presentation for the LSUIElement accessory app
• keep closing activation-free and preserve AppKit-owned panel lifecycle
• add an architecture regression assertion for the activation contract

Validation

• DEVELOPER_DIR=/Applications/Xcode-beta.app/Contents/Developer swift test --package-path apps/decodex-app
• release bundle build/sign/launch via apps/decodex-app/script/build_and_run.sh --verify
• 10 external-focus open/close cycles via the menu-bar accessibility action: opened=1, closed=0