Add X25519+ML-KEM-768 hybrid key support

[cobycloud]

Summary

• add the X25519MLKEM768 identifier to the shared key algorithm/type enums
• extend the file and local key providers to generate, import, rotate, and expose metadata for hybrid X25519 + ML-KEM-768 keypairs
• expand provider unit tests to exercise creation/import/rotation flows for the new algorithm

Testing

• uv run --directory pkgs/core --package swarmauri_core ruff check . --fix
• uv run --directory pkgs/standards --package swarmauri_keyprovider_file ruff check . --fix
• uv run --directory pkgs/standards --package swarmauri_keyprovider_local ruff check . --fix

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https://chatgpt.com/codex/tasks/task_e_68ea2ebbfd748326a54aaaebf43d0fb3