Feat/wkb rewrite

[wietzesuijker]

Summary

Rewrites the WKB parser from scratch, replacing the @loaders.gl/wkt dependency with direct DataView parsing. Adds a WKB encoder (toWkb) for round-trip capability. Modeled on geoarrow-rs.

Follows up on the review feedback in #44.

What changed

File	What it does
types.ts	WkbType enum (1-6), Dimension enum, coordSize()
header.ts	ISO WKB + EWKB header parsing (endianness, type, dim, SRID)
capacity.ts	Pre-calculate buffer sizes from WKB structure without parsing coordinates
reader.ts	parseWkb(data): two-pass (scan + fill), auto-detects type and dimensions
writer.ts	toWkb(data): encodes GeoArrow arrays to ISO WKB (little-endian)

What's new vs the old parser

• Zero dependencies: @loaders.gl/wkt and @loaders.gl/schema removed
• All 6 OGC types: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon
• Auto-detect: geometry type and coordinate dimensions read from WKB header (no caller args)
• EWKB: PostGIS extended WKB with SRID and Z/M flags
• Null handling: Arrow validity bitmap instead of throwing
• Round-trip: toWkb(parseWkb(wkb)) produces identical bytes
• Bounds checking: malformed WKB throws instead of allocating unbounded buffers

Round-trip tested against geoarrow-data fixtures for all 6 types.

AI (Claude) supported my development of this PR.

[kylebarron]

This is cool but not really reviewable as one big PR. If you want to work on this for geoarrow-js, I think we'd need to start with

• a dedicated PR with a detailed markdown description of the work plan, and for example of how the different parts of geoarrow-rs are planned to apply to geoarrow-js
• A series of bite-size PRs that each solve one part of the plan.

There's also part of the TypeScript design that needs some thought. Like here

      const cap = capacity as PointCapacity;

an effective type driven design should never have a cast like this. This can be managed by overloads, discriminated unions, etc.

[wietzesuijker]

Makes sense. Converting to draft. I opened an issue with the work plan, geoarrow-rs mapping, and a proposed fix for the type casts: #46.