IdentityMapper v0.32.1

Protocol specification documentation patch.\n\n- Expanded docs/identitymapper-protocol.md into IdentityMapper Protocol 1.0 Draft.\n- Added source provider contract, target mapper contract, mapping rules, compatibility rules, identity invariants, and non-goals.\n- Added docs/compatibility-matrix.md with the verified 14 x 14 projection coverage.\n- Updated the README to state the protocol boundary and distinguish IdentityMapper from LDAP wrappers, OAuth wrappers, and authentication servers.\n- Tests: 723 passed.