randy
53c9a82af2
Replaces "regenerate for the current viewport" with what Locus/OsmAnd- style apps give you: tick which countries you want offline (a Natural Earth-derived checklist, public domain, vendored), Apply rebuilds offline.pmtiles/terrain.pmtiles to cover the whole selection at once. Multiple regions can be offline simultaneously (e.g. Slovakia + Austria for a trip that crosses the border) — the selection itself is the source of truth (data/offline_regions.json), not a set of per-country files, so "remove a country" and "refresh a country" are both just "change the selection, then Apply." Confirmed against go-pmtiles' own source (not just its docs) before committing to this shape: `extract --region=<geojson>` treats a FeatureCollection's features as their union already (no dissolve/union math needed on our side — pmtiles/region.go's UnmarshalRegion just concatenates every feature's rings), and `merge` hard-errors on any overlapping tile id between inputs (merge.go's prepareInputs). That second fact rules out "extract each country separately, merge them all" — adjacent countries' region-extracts would share border tiles, since extraction copies whole tiles rather than clipping vector content to the polygon. The actual fix: extract per *source archive* (the Protomaps build, each intersecting Mapterhorn chunk), each call covering the whole current selection via one --region= file — the terrain pipeline already extracted-then-merged per source this way, it just needed a multi-country region instead of a single bbox.