Spec: Ownership and borrowing draft

[JROChub]

Context

• The vision calls for safe, high-performance systems programming, but the spec lacks ownership/borrowing rules.

Goal

• Draft a clear ownership and borrowing model in the spec so contributors can reason about memory safety.

Proposal

• Add a new section in SPEC.md (or a focused appendix) that defines:
  • Ownership, moves, and copies.
  • Borrowing rules (mutable vs immutable).
  • Aliasing guarantees and lifetime model.
  • Diagnostics expectations for common mistakes.
• Include 3-5 code examples showing valid/invalid patterns.

Acceptance criteria

• Spec section exists with terminology and core rules.
• Examples compile as Roc snippets (even if not yet implemented).
• Open questions are called out explicitly.