v2.9.0 — asr-canary verbose_json with timestamps

Return OpenAI Whisper-shape verbose_json (segments + words) for
canary-180m-flash and canary-1b-flash. Plus srt + vtt subtitle
output built from segments. SALM-based canary-qwen-2.5b stays
text-only (no timestamp head).

Whisper-only segment fields (avg_logprob, no_speech_prob,
compression_ratio, tokens) are null-filled so existing whisper
clients work unchanged.

Live e2e tests (verbose_json + srt) added — asr-canary 8/8 green.