Implement XMPP gateway and expose agents' capabilities

[romanbsd]

Summary by cubic

Adds an optional XMPP gateway that exposes selected agent operations to external XMPP callers. Previously the agent had no XMPP surface; with XMPP_COMPONENT_ENABLED=1, the agent now starts a XEP-0114 component gateway, advertises an explicit export-tool manifest, and executes tasks with progress, cancellation, and PostgreSQL-backed state.

New Features

• New export-tools subsystem allowlists agent operations (ping, handle_crm_request) exposed through authenticated internal HTTP routes.
• New @agent-xmpp/protocol, @agent-xmpp/core, and @agent-xmpp/gateway packages implement ProtoXEP schemas, JSON validation, stanza codecs, discovery, presence, receipts, chat states, and task invocation.
• Task state persists in XmppAgentTask for 24 hours and supports replay and cancellation.

Migration

• Requires bun install and the new Prisma migration 20260826190000_xmpp_agent_tasks.
• Set the XMPP_* env vars from .env.example; the XMPP server must contain the component account.
• XMPP_ALLOWED_CALLER_DOMAINS limits discovery and invocation; an empty XMPP_ALLOW_DESTRUCTIVE_CALLERS denies all destructive exports.

^{Written for commit f2905b2. Summary will update on new commits.}

[vercel]

@romanbsd is attempting to deploy a commit to the Comp AI - PoC Team on Vercel.

A member of the Team first needs to authorize it.