feat(three): add voxel boolean operations and interactive spec example

[aka-blackboots]

Motivation

• Provide an end-to-end boolean workflow that can combine any mesh-backed OpenGeometry shape (cuboid, cylinder, sphere, wedge, opening, sweep, polygon-derived meshes) into a new resulting shape with configurable operation semantics.
• Prefer a robust, dependency-free approach inspired by the RobustBoolean paper that uses stable occupancy classification to avoid fragile triangle-triangle clipping degeneracies.
• Expose the capability via the existing JS/Three bindings and the opengeometry-three package so examples and higher-level tooling can consume the result.

Description

• Added a voxel-backed boolean implementation and API booleanOperation(left, right, options) which returns a BooleanShape (see main/opengeometry-three/src/operations/boolean.ts) and supports union, subtract, and intersect with options gridResolution and constrainResultToPositiveY.
• Exported the operations via main/opengeometry-three/src/operations/index.ts and updated package entry exports in main/opengeometry-three/index.ts so the API is available from @og-three.
• Added a runnable Vite example and reusable example builder: examples-vite/operations/boolean.html, examples-vite/src/pages/operations-boolean.ts, and src/examples/boolean.ts, and surfaced a catalog card in examples-vite/index.html.
• Documented the implementation and handoff in AI-DOCs/2026-03-04-boolean-operations-implementation.md including rationale, how it maps to the RobustBoolean approach, usage notes, and caveats.

Testing

• Ran cargo fmt --manifest-path main/opengeometry/Cargo.toml --all and it completed successfully.
• Ran cargo check --manifest-path main/opengeometry/Cargo.toml and it completed successfully (Rust build checks passed with warnings only).
• Ran cargo test --manifest-path main/opengeometry/Cargo.toml and all repository unit tests passed (14 library tests + 3 primitives smoke tests; all OK).
• Ran npm --prefix main/opengeometry-three test which executed the package-level test script and returned (note: package-level test is a noop by design and completed successfully), while npm --prefix main/opengeometry-three run build-example-three failed in this environment because the WebAssembly package main/opengeometry/pkg/opengeometry (the built wasm artifacts) is not present so Vite cannot resolve ../opengeometry/pkg/opengeometry, therefore the example build is blocked until the wasm package is produced (residual risk: example bundling and runtime wasm resolution depend on the built wasm artifact).

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Codex Task