Copilot instructions

1---
2applyTo: "src/coreclr/**,src/native/corehost/**"
3---
4 
5# Core runtime
6 
7Conventions for CoreCLR and native host changes. Also apply `conventions`, the language file
8(`csharp` or `native`), `tests` for test changes, and `jit` for JIT changes.
9 
10## Correctness & Safety
11 
12- **Prefer correct-by-construction designs.** Prefer designs that are correct by construction (e.g., scanning IL) over manually maintained parallel data structures. A missed optimization is better than silent bad codegen.
13- **Allocate on the correct loader allocator for collectibility.** When allocating runtime data structures for generic instantiations, use the correct loader allocator accounting for collectibility of type arguments.
14 
15## Performance & Allocations
16 
17- **Avoid LINQ and records in low-level compiler codebases.** In CG2/ILC and AOT tools, use direct loops instead of LINQ and readonly structs instead of records. Use concrete types over interfaces in private code.
18