feat(render-parity): add deterministic frame comparison tool

- Introduced `render-parity` crate for comparing rendered frames against reference images.
- Added command-line options for specifying manifest and output directory.
- Implemented image comparison metrics: mean absolute difference, maximum absolute difference, and changed pixel ratio.
- Created a configuration file `cases.toml` for defining test cases with global defaults and specific parameters.
- Added functionality to capture frames from `render-demo` and save diff images on discrepancies.
- Updated documentation to include usage instructions and CI model for automated testing.

crates/render-parity/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "render-parity"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+image = { version = "0.25", default-features = false, features = ["png"] }
+serde = { version = "1", features = ["derive"] }
+toml = "0.8"