Track allocator and free provenance #26

Goal

Track allocator provenance for allocation-owning values and enforce safe deallocation across semantic and LLVM boundaries.

Completed

• Added allocator descriptors to owning dynamic arrays and strings.
• Added allocator-aware allocation, release, drop glue, and automatic cleanup.
• Consumed owned values passed to alloc; allocator is sized and equatable.
• Kept carrier-only array/string ABI paths free of unnecessary allocator runtime symbols.
• Centralized owned-interface ABI layout and separated owned/borrowed interface symbols.
• Fixed borrowed-interface thunk receiver lowering.
• Rejected owner-bearing extern parameters and returns with T0021.
• Added raw-pointer FFI fixtures and cross-module owned ABI coverage.
• Made synthesized allocator bridge symbols module-local to avoid duplicate definitions.

Evidence

• Commits: 53c5432, ea925f1, d651bda.
• Full Go tests, vet, bundle generation, positive runtime fixtures, negative semantic fixtures, and git diff --check pass.
• main is synced to origin/main.

Future boundaries

• Owner-bearing values must not cross arbitrary FFI; use explicit raw-pointer adoption/release APIs.
• Scoped/custom allocator instances and portable runtime bridge replacement remain future design work.
• See Add scoped and custom allocator behavior #64 for separate allocator-behavior/lowering follow-up.