Salvaged from #6600 (@kristianvast) — re-scoped to the voice half only and
rebased onto current main. The cascading-interrupt hang half of the original
PR landed independently in dd0d1222a, so this carries ONLY Problem 1.
When a voice/audio message arrives while the agent is busy on the same
session, it hit the interrupt path with empty text because STT only ran after
the running-agent guard — the voice was effectively lost. Now we transcribe
audio BEFORE signaling the agent (and on the fresh-message path), echo the raw
transcript back to the user (🎙️), and _enrich_message_with_transcription
returns (text, transcripts) so callers can echo. A new
_dequeue_pending_with_transcription drives the post-agent drain the same way.
Reapplied onto _prepare_inbound_message_text (inbound enrichment was extracted
from the inline dispatch block since the original PR).
Co-authored-by: Kristian Vastveit <kristian@agrointel.no>
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