@wp.func_native passes tile parameters by value instead of by reference #1362

Description:

When using @wp.func_native with tile parameters, the generated C++ code passes tiles by value rather than by reference. This means native snippets cannot modify shared tiles in-place — any writes to a tile parameter inside a native snippet operate on a copy and are silently discarded.

@wp.func already passes tiles by reference (using C++ template parameters and non-const references), but @wp.func_native's codegen_snippet() does not apply the same treatment. This inconsistency prevents users from writing native tile operations that mutate shared state, such as fused tile primitives that update a shared velocity vector.

Expected behavior: Tile parameters in @wp.func_native should use the same pass-by-reference semantics as @wp.func, allowing native snippets to read and write tile data directly.

Affected code: warp/_src/codegen.py — codegen_snippet() method.