d2sketch: upgrade to Rough.js 4.6.6

[alixander]

Depends on: d2lang/rough-go#2

Summary

• upgrade D2 sketch rendering from the Rough.js 4.0.4-compatible native port to the D2-used Rough.js 4.6.6 surface
• update Rough.js, hachure-fill, and path-data-parser attribution and notices
• accept the deterministic seeded sketch-path changes from Rough.js 4.6.6

Compatibility

This changes seeded sketch SVG path data. It does not change diagram layout, board JSON, IDs, text, style semantics, or the non-sketch renderer.

The accepted update contains 40 SVGs: 33 focused d2sketch fixtures, 6 E2E fixtures, and 1 CLI fixture. Thirty-six keep identical SVG structure and path counts while updating only path data. The other four are the light/dark arrowhead and crow's-foot matrices, where current Rough.js emits fewer internal paths for filled markers; visual review confirms the rendered markers remain intact.

The dependency is the signed rough-go v0.2.0 release, which targets the merged native-port PR exactly.

Validation

• official Rough.js 4.6.6 npm oracle: 1,000 randomized D2-profile calls
• every rough-generated path in D2's focused sketch suite matches official Rough.js 4.6.6 after D2 serialization
• CI=1 go test -mod=readonly --timeout=30m -count=1 ./...
• focused go test -race, full go vet, native build, and Go WASM build
• D2.js build plus 39 Bun unit tests and 2 CJS/ESM integration tests
• all 40 accepted SVGs parse and contain no NaN/Inf output