Store Skip launcher in the VM workspace

[themartiano]

What changed and why

Deleting the VM workspace previously left Skip launcher enabled in macOS preferences. Store the choice in a versioned launcher-settings.json file in the selected VM workspace, defaulting to off when the file is missing or invalid. Always show the launcher when there is no existing VM disk, including disposable sessions, even if a settings file remains.

Ignore the old UserDefaults value, so existing users must enable Skip launcher again. Custom locations and environment overrides select their own setting; release and development apps sharing a workspace share the choice. Choices made before first launch are retained after the storage backend initializes the workspace, keeping empty custom folders usable. Save errors restore the toggle and explain the failure.

Testing

• swift test --package-path macos --disable-sandbox --filter 'StartupPreferenceStoreTests|StartMenuStartupTests|GuestBootFixTests': passed, 22 tests across 3 suites (with repository-local Swift/Clang module caches).
• make test: passed on Apple Silicon macOS, including 408 Swift tests and the guest, contract, shell, and disk-resize suites. The initial sandboxed run failed local socket tests with Operation not permitted; the unrestricted rerun passed.
• git diff --check: passed.
• No manual VM boot or packaged-app launch was performed; AppKit tests cover startup confirmation, toggle rollback, and save-error presentation.