[appujet]

Summary

Fixes audio being cut off or glitched at track ends and on join/reconnect.

Changes

• Don't send the speaking-stop (empty mask op 5) when audio ends. It can cut off the tail of a track.
• Hold audio until the DAVE key ratchet is ready, and send silence meanwhile. Audio could previously go out unencrypted.
• Re-announce speaking on op 4 (SESSION_DESCRIPTION).
• Announce speaking only after a successful send.
• Drop zero-length frames instead of sending them.

Tests

Added unit tests for each change. cargo fmt, clippy and test pass.

Manual testing

• Track end has no cut-off or pop
• Join and reconnect with DAVE is glitch-free