IdentityMapper v0.35.3

Protocol versioning RFC patch. Adds RFC 0003 for IdentityMapper Protocol Versioning, separates IdentityMapper Protocol 1.0 from the Python reference implementation version, documents major/minor protocol rules, implementation/document patch semantics, and breaking vs non-breaking protocol changes. Compliance suite now declares IdentityMapper Protocol 1.0 Draft as its target. Core domain, capability contracts, runtime behavior, providers, and target mappers remain unchanged. Verified: 749 tests passed, 5 compliance tests passed, compileall OK.