chore(lambda-rs): Fix all clippy warnings

[vmarcella]

Summary

This PR fixes all compiler warnings across the workspace by cleaning up dead code, unused variables, clippy lints, and deprecated API patterns.

Related Issues

Changes

• Remove unused functions and methods (to_wgpu, into_parts, supports_surface_sample_count, supports_depth_sample_count)
• Add #[allow(dead_code)] annotations where fields are intentionally retained for future use
• Fix unused variable warnings by prefixing with underscore or removing entirely
• Replace explicit iterator loops with idiomatic Rust patterns (for cmd in command_iter.by_ref())
• Convert &Vec<T> parameters to &[T] slice references per clippy recommendations
• Remove unused lifetime parameters from function signatures
• Add Default implementations where new() constructors exist
• Add missing documentation to public API items
• Fix redundant closure patterns (map_err(|e| Error(e)) → map_err(Error))
• Clean up unused imports across examples and tests

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• Feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (updates to docs, specs, tutorials, or comments)
• Refactor (code change that neither fixes a bug nor adds a feature)
• Performance (change that improves performance)
• Test (adding or updating tests)
• Build/CI (changes to build process or CI configuration)

Affected Crates

• lambda-rs
• lambda-rs-platform
• lambda-rs-args
• lambda-rs-logging
• Other: tools/obj_loader

Checklist

• Code follows the repository style guidelines (cargo +nightly fmt --all)
• Code passes clippy (cargo clippy --workspace --all-targets -- -D warnings)
• Tests pass (cargo test --workspace)
• New code includes appropriate documentation
• Public API changes are documented
• Breaking changes are noted in this PR description

Testing

Commands run:

cargo build --workspace
cargo test --workspace
cargo clippy --workspace --all-targets -- -D warnings

Manual verification steps (if applicable):

1. Verified all examples still compile and run correctly
2. Confirmed zero warnings in release and debug builds

Screenshots/Recordings

N/A - No visual changes

Platform Testing

• macOS
• Windows
• Linux

Additional Notes

This is a cleanup PR that addresses accumulated warnings without changing any runtime behavior. All removed code was verified to be unused through static analysis. Fields marked with #[allow(dead_code)] are retained for architectural reasons (e.g., the instance field in RenderContext is kept alive to ensure proper resource lifetimes).