Extract `load_road_transport()` as a shared helper for bus and coach,
combining the near-identical route rendering blocks in `get_trip_routes`
and `Trip.elements()` into single `in ("coach", "bus")` branches.
Document transport type patterns in AGENTS.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Aggregate yearly stats into overall totals so the trip stats page
shows flight segments by airline, airports used, and stations used
in the summary section at the top.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
