Station legibility when trains are nearby

[Jorioz]

What to build

A train approaching a station (progress just below the stopped threshold) currently parks its marker right on top of the station dot, making it hard to see whether the marker is at, near, or covering the stop. The direction-based lane offset (#21) should resolve most of this since markers will ride beside the centerline rather than on it — this slice verifies that and adds the remaining polish so stations stay legible whenever a marker is close: e.g. a halo/ring around the station dot, or fading/de-emphasizing the dot while a marker is within range. Pick whichever reads best after #21 lands.

Acceptance criteria

• A train at high progress toward a station no longer visually obscures the station dot
• Station dots remain clearly identifiable when one or more train markers are adjacent
• The station's hover/click behavior is unaffected by a nearby train marker
• Verified visually at typical zoom levels for both a train approaching a stop and two trains flanking a stop

Blocked by

• Direction-based lane offset for train markers #21 (the lane offset changes what remains to fix here)