Prototype: extract offline hiking trails from the Geofabrik PBF we already have

No custom Planetiler profile needed after all — Maptool::HikingTrails
runs osmium tags-filter r/route=hiking against the same .osm.pbf
PmtilesBuilder already downloads per country for offline.pmtiles, then
osmium cat -f opl (locations_on_ways=true) to get member-way geometry
back as plain text, no separate node-id lookup table to build.

No general OSM tool stitches a route relation into one line (routes
are a semantic grouping, not a geometry type) — parse_opl does that
walk itself, same as the Overpass-based click handler already does
client-side. Kept pure/testable apart from the two osmium subprocess
calls, mirroring OverpassPois.fetch vs .to_geojson.

rake hiking:trails[pbf,out] to try it by hand against a real cached
extract. Not wired into the actual offline build or rendering yet —
still just a prototype, per TODO.adoc.

TODO.adoc

@@ -12,7 +12,8 @@ independence from connectivity.
 * [x] Shaded relief / DEM layer — hillshade toggle in the sidebar, sourced from public Terrarium tiles online; reads `data/terrain.pmtiles` for offline if one's been generated (see docs/development.adoc), otherwise the toggle is online-only for now
 ** [ ] Terrain slope readout for parking (numeric, not just visual shading)
 * [ ] Contour lines from OSM for hikes and mountain passes
-* [x] Hiking trail overlay — Waymarked Trails raster tiles (`public/js/hiking_trails.js`), colored per-route by the OSM `colour` tag they already render (the KST/KČT paint-blaze colors in Slovakia/Czechia, plain red elsewhere), so no styling logic needed here. Online only for now — an offline copy (baked into `offline.pmtiles`, needing a custom Planetiler profile for route relations) is deferred until there's a route planner/router to pair it with
+* [x] Hiking trail overlay — Waymarked Trails raster tiles (`public/js/hiking_trails.js`), colored per-route by the OSM `colour` tag they already render (the KST/KČT paint-blaze colors in Slovakia/Czechia, plain red elsewhere), so no styling logic needed here. Click queries a one-off Overpass `around` search (racing 3 public mirrors) for the route's name/colour/network/operator/distance, no server involved
+** [x] Prototype: an offline extraction path exists after all, no custom Planetiler profile needed — `Maptool::HikingTrails.extract` (`lib/maptool/hiking_trails.rb`, `rake hiking:trails[pbf,out]`) runs `osmium tags-filter r/route=hiking` + `osmium cat -f opl` against the *same* Geofabrik `.osm.pbf` already downloaded for `offline.pmtiles` — no new download, no new dependency. Not wired into the actual offline build/rendering yet, still deferred until there's a route planner to pair it with (see the entry above)
 * [x] Overpass/OSM scripts to extract POIs (drinking water, dump stations, LPG, public toilets, laundromats, shops, springs) — `rake overpass:pois`, see docs/development.adoc; writes a `.geojson` to drop in `data/gpx/` or upload. Also runnable from inside the app itself now, see the import plugins entry below (`plugins/overpass-pois` wraps this same query). Each category now carries a real `POI_ICONS` glyph and color (not p4n2gpx's plain red marker) plus a popup description built from opening_hours/operator/website tags
 * [x] Import plugins: a pluggable way to add more data sources (Park4Night, iOverlander, Freecampsites, ...) without their scrapers necessarily living in this (public) repo — sidebar icon (logged in only) lists whatever's under `plugins/`, "Run for this area" uses the current map viewport as the bbox, no separate area-picker needed. Contract: a `plugin.json` manifest + a script that reads `--south`/`--west`/`--north`/`--east` and prints a GeoJSON `FeatureCollection` to stdout (`lib/maptool/plugins.rb`, `GET /api/plugins`, `POST /api/plugins/:name/run`) — output saved the same way an upload would be. `plugins/overpass-pois` ships as the reference example; a private/ToS-sensitive scraper just drops its own directory in locally and is never `git add`ed
 ** [x] Park4Night — private plugin (`data/plugins/p4n2gpx/`, outside this repo per the "ToS-sensitive scraper" note above); iOverlander/Freecampsites still open, same story