* feat(agentmail): add AgentMail integration with 21 tools
* fix(agentmail): clear stale to field when switching to reply_message operation
* fix(agentmail): guard messageId and label remappings with operation checks
* fix(agentmail): clean up subBlock titles
* fix(agentmail): guard replyTo and thread label remappings with operation checks
* fix(agentmail): guard inboxIdParam remapping with operation check
* fix(agentmail): guard permanent, replyAll, and draftInReplyTo with operation checks