fix(debug): draw the region a coverage switch asked for

Switching region fires three requests for it. Two carry the previous
viewport: the badge row resizes, the map's ResizeObserver calls
invalidateSize, and the moveend that follows reports the old bounds under
the new region. Only the third carries the boundary, and it is the oldest
of the three, so the stale-response guard threw it away -- leaving the
outline undrawn, the map parked on the region before it, and every
panorama out of view.

The boundary is now applied on the region it describes rather than on
request order.

Also adds a project .ckignore so src/app/debug/coverage/ reads as the
application source it is rather than a test-coverage report directory.

.claude/.ckignore

@@ -0,0 +1,5 @@
+# Project override for the shipped scout-block baseline.
+#
+# src/app/debug/coverage/ is application source -- the debug page that draws
+# the panorama index on a map -- not a test-coverage report directory.
+!coverage