Show update alert when checking from menu bar with no window open

[sapsaldog]

Problem

When the app runs as a menu-bar accessory with no window open, clicking Check for Updates did nothing visible — no "Checking…" window, no "You're up to date" alert, no error.

Root cause

Sparkle's SPUStandardUserDriver shows its "Checking…" status window and result alerts (up-to-date / errors) as transient panels. WindowObserver.isAppWindow deliberately does not count Sparkle's panels as app windows, so when the "Checking…" window closes, WindowObserver reverts the activation policy to .accessory. That deactivates the app, and on macOS 14+ cooperative activation (NSApp.activate()) will not refocus an app without a recent user interaction — so the result alert opens behind other apps' windows, invisible.

Fix

Hold the app in .regular and activate it for the full duration of a user-initiated update session:

• DockPolicy.activationPolicy gains an updaterSessionActive input (→ .regular while a session runs), plus updaterSessionActiveKey and an updaterSessionActive(from:) notification-payload parser.
• UpdaterManager.checkForUpdates() posts .updaterSessionStateChanged(active: true) and calls NSApp.activate(ignoringOtherApps:) inside the click event (the activation must be tied to the user interaction — Sparkle's own later attempt is not enough). A private UpdaterSessionDelegate (SPUUpdaterDelegate) clears the session in updater(_:didFinishUpdateCycleFor:error:); Sparkle holds the delegate weakly, so the manager retains it.
• WindowObserver observes the notification, tracks the session flag, and re-evaluates the activation policy.

Verification

• Live: with no window open, Check for Updates now brings the app to front and shows the "You're up to date!" alert on top.
• ✅ Full unit suite (481 tests) passes
• ✅ SwiftLint clean
• ✅ 100% coverage gate passes — the new arg + parser are covered by DockPolicyTests

🤖 Generated with Claude Code