"""Ask Helix — the employee-facing assistant channel.

A cross-domain orchestration layer (like ``app/intelligence``), not a business
domain: it owns no tables of record, and reaches business capability only
through surfaces that already enforce their own RBAC, audit and idempotency.

PR1 ships the transport half — Feishu event intake, sender identity and the
release gate. The conversation kernel (session state, model turn, tool calls)
lands on top of it in the following slice; until then an authorized sender
receives a deterministic readiness reply and no model is ever called.
"""