fix(voice): clear the stale user turn when resuming a false interruption

[saime428]

Fixes #7063

When a false interruption is confirmed and the paused agent speech resumes, _on_false_interruption never discards the recognition turn that triggered the pause. For a VAD-only turn (nothing committed by STT) that means _speech_start_time survives the resume. AudioRecognition only sets that anchor while it is None, so the next real utterance inherits the old one, and the committed ChatMessage ends up with a started_speaking_at from before the agent even resumed speaking. Sorting a transcript by timestamp then puts the user line in the wrong place. The issue saw a 12 second offset in production.

The change calls _clear_user_turn() at the top of the resume branch, before agent speech restarts. That is the same discard path the public clear_user_turn() API uses, so the dropped turn's transcript buffer, timing anchors and turn tracker all go together. Two cases that might look risky are fine: the resume callback cannot fire while the user is talking, because a new START_OF_SPEECH cancels the false-interruption timer, and a committed turn cancels the timer on its own path before the callback ever runs.

Added test_resume_discards_the_stale_recognition_turn to the existing false-interruption suite. It fails on main and passes here.

Tested with uv run pytest tests/test_false_interruption_resume.py --unit (10 passed) and the full uv run pytest --unit gate (1901 passed, no new failures compared to main). make check is clean apart from a pre-existing mypy complaint about the missing boto3 stub in the aws plugin.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

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