Add PathStyleExtension Seattle road data

[chrisgervang]

Goals

Publish the pinned Seattle street-design snapshot used by deck.gl's new PathStyleExtension example, together with the tools needed to audit and regenerate it.

Changes

• add a compact, render-ready Dexter Avenue N and Thomas Street snapshot with normalized path and polygon assets
• consolidate compatible road context into ordered surface and detail collections while preserving every asset
• co-locate the ArcGIS extraction, validation, and candidate-site scoring tools with the data
• generate provenance manifests and audit reports locally while keeping those reproducible artifacts ignored
• precompute geometry classification, dimensions, dash patterns, source links, and tooltip fields instead of shipping raw source layers
• validate source geometry, optional provenance, render assets, derived lane bands, justified crosswalk guides, and stitched pavement-symbol paths
• document the source data and PDDL 1.0 license

Validation

• node examples/path-style-extension/scripts/validate-seattle-road-diagram.mjs
• clean extraction; extraction gate passed with 794 source features and produced 1,031 render assets across 9 collections
• validation of freshly extracted output with provenance checks and of the committed snapshot without a manifest
• node --check for all three scripts
• node examples/path-style-extension/scripts/score-candidate-sites.mjs