With RUDDER_AUDIO=browser the engine records no local microphone. The page
captures the reader's mic, converts it to 16 kHz mono PCM in an AudioWorklet,
and streams it over a WebSocket at /api/rudder/stream into the same speech
session a local recorder feeds. The words come back on that socket to that
reader only, never on the shared event stream. One session at a time; a second
reader is told the engine is busy. The engine honours RUDDER_HOME, accepts the
public host named in RUDDER_ALLOW_HOST, and refuses a socket from another
origin. The dev proxy now carries WebSockets to backends.
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