Directional, clickable mini dots for stopped trains

[Jorioz]

What to build

When a train is stopped at a station it renders as a plain circle (mini dot) under the station label, which hides which way the train will depart. The departure heading is already computed for stopped trains in the marker geometry — it is just discarded because the full marker is hidden while stopped.

Plumb that angle through to the mini dot and render it as a small rotated chevron using the same polygon shape as the moving-train marker, so the visual vocabulary stays consistent (small chevron = stopped train, large chevron = moving train). Apply the same treatment at Union station's mini dot row. Additionally, make each mini dot individually clickable: clicking a mini dot selects that specific train (same behavior as clicking a moving train marker), rather than only being able to select the station.

Acceptance criteria

• A stopped train's mini dot is a small chevron pointing in its departure direction
• Union station mini dots get the same directional treatment
• Clicking a mini dot selects that train and opens the train info box view
• Clicking the station dot/label still selects the station as before
• Mini dot enter/exit animations and per-line coloring keep working

Blocked by

None - can start immediately