feat(plugins): update installed registry plugins after TablePro updates

[datlechin]

Why

Registry plugins only updated when someone clicked Update, and Activate Now kept running the old build: a loaded Swift bundle cannot be unloaded, and Bundle(url:) returns the cached instance for the same path.

Change

• After a TablePro update, user-installed registry plugins older than the app update by themselves. A rejected plugin installs and loads at once; a loaded one downloads to PluginStaging/Updates/<id> and is swapped in at the next launch, before discovery.
• The row reads "Updates when TablePro restarts" until then. A file installed over a registry plugin stages the same way and drops its registry sidecar.
• No newer build yet retries at 30 s, 300 s, 600 s, 5 attempts. Debug builds never run the pass. A connection waits only for the pass's rejected-plugin repairs.
• Removed the update badge, Update, Activate Now, On Quit, the network monitor and PluginManager.init's unused userDefaults.

Verified

PluginRegistryUpdatePassTests, renamed from PluginManagerReconciliationTests, runs the pass against a stubbed manifest and installer. Changed on purpose: DebugUpdateGateTests (no network monitor), and ensurePluginReadyNoopForUnknownType dropped (a no-op in Debug). Deleted with their code: PluginInstallTrackerStagedTests, PluginInstallerCoalescingTests, the PluginBundleVersionTests hot-swap and bundleShortVersion cases.

Not in this PR

• Merges in the freeze window with steps 20-23.
• Offline at launch, the pass stops after 5 tries and a reconnect does not restart it; connecting repairs a rejected plugin. A long-wait fetch for the pass belongs in RegistryClient.swift.
• Docs: docs(features): describe plugin updates after a TablePro update docs#36 (merged), docs(features): say when a file-installed plugin updates from the registry docs#38.