Delete/Plan for Assimp-Rust

**Describe the technical debt**
Assimp Rust is not currently usable, as it does not actually interface with C++, and is mostly a scaffold.
What did exist seems to be half-baked.

**Better solution**
A clear and concise description of what you would expect.

Either delete it, or merge with Russimp

**Additional context**
If a clear plan is described for Assimp_rs I can implement parts of it.

Start by comparing the existing Assimp Rust scaffold with Russimp and verify whether Assimp Rust interfaces with C++ as described. Decide whether the project should be deleted or merged, then document a clear implementation plan; done means the repository has an agreed direction and actionable scope.

Written by the indexing model from the issue text.