Arma tiles agent guide

Keep source/ in version control through .gitkeep, but never commit .kml or .kmz inputs. They are deployment data mounted through ARMA_TILES_SOURCE_DIR.
The generated result belongs in tiles/; do not hand-edit it. Run docker compose up --build or ./scripts/build-tiles.sh to regenerate it.
Preserve the public Arma endpoint format: /tiles/{x}/{y}/{z}. Internal files remain tiles/{z}/{x}/{y}.png.
CALLBACK_PROVIDER is optional. When set, it must be an HTTPS template containing exactly {z}, {x}, and {y} in its path. Validate it before a tile build; no provider-specific host or branding belongs in application code or documentation.
With a callback provider, MapLibre uses only /tiles/{x}/{y}/{z}. The builder flattens Arma overlays over callback tiles, so transparent edges never expose black pixels.
Keep source processing idempotent, do not modify input files, and preserve per-source error reporting in tiles/metadata.json.
Before handing off changes, run python3 tests/test_build_tiles.py, docker compose config --quiet, and docker compose build tiles when Docker is available.