kornia-rs API flavor

1. Output buffers: image ops are fn op(src: &Image<T, C, A1>, dst: &mut Image<T, C2, A2>) -> Result<(), E>. Validate src/dst sizes first and return a descriptive error on mismatch.
2. Naming: <output>_from_<input> (gray_from_rgb).
3. Dtype dispatch: one generic entry point bound by a sealed trait (e.g. GrayFromRgb) with explicit impls for u8, f32, f64. No blanket impl<T: Float> (conflicts without specialization). See kornia-simd.
4. Generics over concrete: keep Image<T, C, A> generic over allocator and channels (const generics); do not hard-code Vec.
5. Errors: each crate has a thiserror enum; wrap lower-crate errors with #[from]. Fallible constructors (new(..) -> Result<Self, _>).
6. Config structs document units and coordinate frames (pixels vs normalized coordinates, radians vs degrees).
7. Return types: domain structs/Option, not tuples of vectors.
8. Bindings parity: a Rust API exposed to Python (kornia-py/src) or C++ (kornia-cpp/src, include/) must keep the same naming and semantics; add tests on the binding side.
9. Feature gating: hardware-specific code (cuda, gstreamer, v4l, turbojpeg) stays behind features; the default build must compile without.
10. Docs: new public API is not done until it has rustdoc with Arguments, Returns, Errors, Example, and an entry in the crate README and a changelog.d/ fragment when user-visible.