Once the cache was full, every write sorted all 50,000 entries to find the
oldest. A Map keeps insertion order, so keep the map in fetch-time order
and delete from the front: the resolver re-inserts each point it refetches
(an overwrite would leave it in its old place), and the disk load sorts
once, since a file written before this change, or a migrated raw-batch
cache, is not in age order.
Suggested by asturksever on #975.
Use 64-point browser and upstream terrain batches to reduce cold-cache timeouts. Preserve successful chunk results, distinguish absent readings from malformed responses, and reject fabricated zero heights.
Original terrain resilience contribution by ItzDESTAQ, with browser batching, validation and regression follow-up by Sameh Khamis.
Validated with unit/build/format/boundary checks, 108 tracking checks, 5 terrain-outage checks, controlled slow-upstream comparison and live browser checks.
Co-authored-by: ItzDESTAQ <[email protected]>
Co-authored-by: Sameh Khamis <[email protected]>
daikaginza