ui: tighten the badge/dock/tour probes after review and fix the tour's stale hole

The session old-file probe and save_scheduled now discriminate, Esc is read through the real key path, the dock-section probe proves the Measure section starts out of view, and the tour's spotlight is measured independently of the helper it is drawn from. A target scrolled out of its scroller no longer leaves the previous hole standing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ui_app.hpp

@@ -2127,7 +2127,8 @@ void tour_update(TourView& view);
 /// The widget the current stop points at, or nullptr when the walk is not on a stop.
 GtkWidget* tour_target(TourView& view);
 /// The part of `target` that is on screen, in `overlay`'s coordinates: its bounds intersected with every
-/// scrolled window above it. False when it cannot be measured yet or is scrolled out of sight entirely.
+/// scrolled window above it. A target scrolled out of sight entirely is measured and *empty*: true with a
+/// zero-size rectangle. False only when it cannot be measured yet (no allocation, not in the overlay).
 /// The spotlight is drawn from it, and the probe reads the spotlight against it.
 bool tour_target_bounds(GtkWidget* target, GtkWidget* overlay, graphene_rect_t* out);