Adds ambientPositionProvider (never calls LocationSource.stop(), only the
idempotent start()) and wires it into ShellScaffold whenever no trip is
active, so the persistent background map centers and follows the device's
live GPS position at street-level zoom instead of sitting at (0,0)/zoom 2
until a recording starts. RideMap gains an ambientPosition param that the
existing chase-camera/pan-cancel/location-marker logic falls back to
whenever there are no recorded points, with recorded points always taking
priority. Also brings in the docs/feedback ticket set (FB-01..FB-05, README,
FEEDBACK.md) that this worktree's branch point predated.
Adds 10 tests (374 -> 384): RideMap-level ambient centering/chase/pan-cancel/
marker coverage in test/ride_map_test.dart, plus shell-wiring and
provider-level (never-calls-stop, mapEnabledProvider-off) coverage in
test/widget_test.dart. flutter analyze remains clean.
Removes the idle GlassPanel/BigStat Speed-Status-Last ride block from
RecordScreen; the live map plus START control is now the entire idle
screen. HudEditOverlay is gated on !ui.isIdle. Migrates the five
affected widget tests to seed a recording trip and assert against the
HUD's own ValueKey(HudMetric.speed) widget instead of the old idle
Key('speed').
Also fixes a pre-existing gap this migration exposed: _HudMetricValue
had no mounted-mode awareness at all (no text scaling, and its
per-metric accent colours fall just under AA contrast against the
mounted theme's GlassPanel surface). Adds scale and mountedMode
params, reusing BigStat's own mechanisms (scale multiplier, explicit
onSurface ink) to fix both.
