feat(ios): alert when active connection is deleted mid-session

[datlechin]

Summary

Small UX win extracted from a P1 navigation refactor experiment that did not pan out (iOS 26 TabView and per-tab NavigationStack tug over the navbar surface, so the canonical Apple pattern is unusable here for now).

What lands:

• When the connection currently shown in ConnectedView is removed from appState.connections mid-session (for example via iCloud sync from another device), an alert appears: "This connection no longer exists. It may have been removed from another device.". Tapping OK calls dismiss(), which pops back to the connection list on iPhone or clears the detail column on iPad. Without this, the next data action would fail with a generic error and the user would not know the connection vanished.
• Internal: ConnectionCoordinator.navigationPath renamed to tablesPath. Only the Tables tab actually drives drill-down (TableInfo → DataBrowserView), so the new name reflects intent. navigateToPendingTable() and the NavigationStack(path:) binding are updated atomically.
• Internal: drop the duplicate .navigationTitle("Info") on ConnectionInfoView. ConnectedView.tabTitle() already returns "Info" for the Info tab and applies it on the outer NavigationStack.

Test plan

• Open Connection A on iPhone, navigate into a table, then delete Connection A from another device with iCloud sync on. iCloud sync arrives, alert appears, OK pops back to the connection list.
• Same scenario on iPad: detail column clears to the empty state.
• Deep link tablepro://connect/<uuid> → pendingTableName push still works (uses tablesPath.append(table)).
• Info tab navbar title still reads "Info" with the pencil edit button to its right.