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.
