A brand-new route (or one with fewer than two pins) now falls back to the
ambient GPS position for its initial map center instead of (0, 0) in the
middle of the ocean, reusing FB-01's ambientPositionProvider. Routes with
one or more real waypoints are unaffected. Falls back to (0, 0) as before
when no ambient fix is available.
Adds three widget tests covering the fixed-fix, no-fix, and
real-waypoint-wins cases. Emulator verification was attempted but the
Android emulator became unresponsive partway through and was abandoned
per the ticket's conservative-use guidance; details in the ticket's
Outcome section.
