agent: Add initial support for hybrid ECC+PQC decryption with KEM.
* agent/agent.h (enum kemid): New. (agent_kem_decrypt): New. * agent/command.c (cmd_pkdecrypt): Support --kem option to call agent_kem_decrypt. * agent/pkdecrypt.c (reverse_buffer): New. (agent_hybrid_pgp_kem_decrypt): New. (agent_kem_decrypt): New.
Now, it only supports X25519 + ML-KEM.
- GnuPG-bug-id: T7014
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>