/debug/ring now takes an optional scene; conversation_arm_incoming
locks it and, after the greeting, queues that scene's local clip
/sdcard/voice/hint_<scene>_l1_0.wav (played back-to-back). For a
scripted offline call CONNECTED skips the gateway/model listen loop
and just waits for hang-up. Scene is cleared in go_idle so a later
dial-out call never inherits it. Validated: greeting 5.05s + WARNING
hint 6.20s from SD on pickup, no gateway/model.
clement
39e0498221