Live CHP traffic incidents statewide, optionally filtered.

Data: the California Highway Patrol statewide computer-aided dispatch
feed - collisions, traffic hazards, disabled vehicles, closures as CHP
logs them. Refreshes about once a minute; incidents disappear when CHP
closes the log. Fetched live on every call.

Filters (combinable):
- highway: a route like "I-80", "US 50", "17", "Hwy 99". Matches
  incidents whose location text mentions that route.
- center: "lat,lon" with radius_km - incidents within that circle. THIS
  IS THE RIGHT FILTER FOR A TOWN OR PLACE NAME: use your knowledge of
  where the place is (e.g. Coyote, CA -> "37.22,-121.74") with radius_km
  15-30. A circle catches every road around the place, not just one
  highway.
- area: substring match on the CHP dispatch-area name. These are CHP
  communication-center names ("Hollister Gilroy", "East Sac", "Golden
  Gate"), NOT town names - do not pass a town here. There is no county
  filter because CHP's feed carries no county field; for a county, use
  center on the county seat with a radius covering the county.

Limits: locations are free-text from dispatchers; a few incidents lack
usable coordinates and are omitted. No history - current logs only.