Fix Tahoe no-window menu bar recovery

[steipete]

Summary

• preserve the app's intended visible status-item names independently of Tahoe's rejected AppKit state
• detect the startup-only no-window failure only when app intent and the persisted enabled visibility default agree
• ignore user-hidden items, menu-manager hiding, stale hidden window records, and pre-Tahoe systems
• add focused startup, defaults, and split/merged lifecycle regression coverage

Validation

• swift test --filter MenuBarVisibilityWatcherTests (36 tests)
• swift test --filter StatusItemControllerSplitLifecycleTests (24 tests)
• make check
• make test (48/48 shards)
• autoreview: clean after fixing stale hidden-window handling

Tahoe 26.5 bundle proof was stopped when the signed test app unexpectedly requested a Keychain password despite all providers being disabled. No credentials were entered and no private Control Center preferences were changed.

Closes #1945