feat(lambda-rs): Add support for indexed draw commands

[vmarcella]

No description provided.

[Copilot]

Pull request overview

This PR introduces indexed draw command support to the lambda-rs rendering engine, enabling more efficient rendering through index buffers and multiple vertex buffer configurations. The changes add a complete API surface for indexed geometry while maintaining backward compatibility with existing non-indexed draw workflows.

• Adds engine-level IndexFormat enum and DrawIndexed command with validation
• Introduces explicit instance ranges to both Draw and DrawIndexed commands (default 0..1 preserves single-instance behavior)
• Implements comprehensive validation for index buffer formats, buffer types, and draw command ordering

Reviewed changes

Copilot reviewed 20 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
crates/lambda-rs/src/render/command.rs	Adds IndexFormat enum with platform mapping and updates Draw/DrawIndexed signatures to include instance ranges
crates/lambda-rs/src/render/mod.rs	Implements validation logic for index buffers, draw commands, and device limits; adds tracking for bound index buffers and current pipeline
crates/lambda-rs/src/render/pipeline.rs	Adds buffer type validation in pipeline builder and device limit checks for vertex buffers/attributes
crates/lambda-rs-platform/src/wgpu/render_pass.rs	Updates platform layer draw methods to accept instance ranges
crates/lambda-rs-platform/src/wgpu/gpu.rs	Exposes max_vertex_buffers and max_vertex_attributes device limits
crates/lambda-rs/examples/*.rs	Updates all examples to include instances: 0..1 in Draw commands
crates/lambda-rs/examples/indexed_multi_vertex_buffers.rs	New example demonstrating indexed draws with separate position and color vertex buffers
docs/tutorials/indexed-draws-and-multiple-vertex-buffers.md	New comprehensive tutorial covering indexed geometry implementation (has type error in example code)
docs/specs/indexed-draws-and-multiple-vertex-buffers.md	Complete specification document for indexed draw feature with API surface, validation rules, and performance guidance
tools/obj_loader/src/main.rs	Updates obj loader to use new Draw signature with instances field
docs/tutorials/*.md	Updates existing tutorial code examples to include instances field
.gitignore	Adds docs/plans/ to ignored directories

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