Trilho public pedestrian graph: preparation method

This bundle offers the complete method used to prepare the derivative walking
network from OpenStreetMap, under ODbL 1.0 section 4.6(b):
https://opendatacommons.org/licenses/odbl/1-0/
The underlying and derivative database are available under ODbL 1.0.
Copyright: OpenStreetMap contributors.
https://www.openstreetmap.org/copyright

Input: Geofabrik Portugal snapshot, OSM timestamp 2026-10-08.
Dated download: https://download.geofabrik.de/europe/portugal-261008.osm.pbf
The original download used portugal-latest.osm.pbf; verify the SHA-256 in
graph-manifest-2026-10-08.json before reproducing this snapshot.
No other datasets or elevation data were added.

Requirements: Python 3.12, curl, pip. On a separate build machine:
  python3.12 -m venv venv
  venv/bin/pip install -r requirements.txt
  curl --fail --location https://download.geofabrik.de/europe/portugal-261008.osm.pbf -o portugal.osm.pbf
  PATH="$PWD/venv/bin:$PATH" venv/bin/python build_graph.py \
    --pbf portugal.osm.pbf --out graph \
    --source-url https://download.geofabrik.de/europe/portugal-261008.osm.pbf \
    --osm-date 2026-10-08

build_graph.py contains the complete import configuration: pedestrian network
only, no driving or bicycle network, no driveways or construction. It fetches
the original Valhalla 3.9.0 graph.lua with a verified SHA-256 and appends the
included public_access.lua before import. public_access.lua contains all
additional access alterations: no ferry routes, no explicitly prohibited
pedestrian access, no private ways without explicit public pedestrian access,
and no private gates. Other pedestrian access rules remain those of Valhalla.
The output includes graph tiles and a provenance/checksum manifest.
The manifest also records the 4.8 km/h walking model; speed is applied at route
calculation time and does not change the imported OSM network.

Valhalla is distributed under the MIT license:
https://github.com/valhalla/valhalla/blob/3.9.0/COPYING
ODbL applies to database rights, not automatically to the software. This free
public preparation method is provided to satisfy the database offer above.
It may be used to reproduce and modify the ODbL database.
The native graph archive can differ by build platform/order; the input and
policy checksums identify the snapshot and alterations. This is not a promise
of identical archive bytes on every platform.
