feat(criteria): add binding-local loss registries

[GBeurier]

Summary

• add the generic DAG-ML process-local implementation registry for Rust closures and provider objects
• expose real local Python callables and JavaScript/WASM functions with exact descriptor resolution and FIT_CV/REFIT attestations
• add a versioned C ABI callback registry with explicit binding identity, lifecycle hooks, error propagation, and descriptor inspection
• pin Python, JavaScript and C conformance fixtures plus training/replay contract closure
• resolve the paired dag-ml-data branch once in CI and use that exact ref in every Rust/Python/WASM job that consumes the peer

Validation

• cargo test -p dag-ml-capi: 100 passed
• cargo clippy -p dag-ml-capi --all-targets -- -D warnings
• Python local registry tests: 11 passed
• WASM Node and web binding smokes
• criteria parity: 7 passed
• training/replay parity: 163 passed
• isolated D4 validator passed
• shared contract validation against the paired dag-ml-data branch passed
• workflow YAML parse, ABI snapshot and contract validators passed

Review

Independent read-only reviews found and resolved two integration issues:

• the checked-in Python extension was stale after Rust binding changes; it was rebuilt and the freshness gate passes
• peer-aware CI was initially applied to Rust/Python/WASM but left an unused default-branch checkout in MSRV; that checkout and its unused environment were removed, preserving MSRV parallelism

Stack

Depends on #22 (controller loss protocol).