Neighborhood verdict

Accepts a point plus free-form life context (household, mobility,
priorities) and returns a ranked verdict: strengths, weak points, and
the one thing to verify in person. Empty context still answers a
generic walk-first daily-needs check and says what was assumed.
Optional radius_m / minutes / mode override what the context implies
(no car / walk-first -> walk, bike -> cycle, car -> drive; default
walk, 15 minutes). Does not call out to extra remote APIs; the
"transit" need additionally reads base/infrastructure transit stops
(bus_stop, subway_station, ferry_terminal, ...) alongside the
places-theme categories, since places alone under-reports bus stops
(#454).

Returns a structured {"error": ...} for bad coordinates, an unknown
mode, a radius past the mode cap, upstream failure, or a degraded
schema. Missing street graph degrades to straight-line times with a
note rather than failing the verdict.