plan(vm): define wide local bytecode

[fffonion]

Summary

• define wide local load and store opcodes while preserving compact short-slot encodings
• carry normalized u16 local slots through VMBC, debugger, interpreter, JIT, native, AOT, wasm, and no-std consumers
• require the completed frame-aware allocation work so wide bytecode addresses only genuine same-frame pressure

Stack

Layer 13 of 14
Previous: #24
Next: #26

Validation

• cargo fmt --all -- --check
• git diff --check