Tracking: optional whispercpp wrapper expansions

[uqio]

This is the tracking issue for whisper.cpp surface that the safe whispercpp API does not (yet) wrap. Each item is a deliberate scope choice — whispery (the in-house consumer) doesn't need it today, and adding it speculatively expands the audited unsafe surface. None of them are blocked; each will be picked up when a concrete caller materialises.

If you have a use case for any item below, comment on the corresponding sub-issue with your scenario.

See whispercpp/TODO.md § 1 for the full rationale.

Sub-issues

• Wrap whisper.cpp's built-in Silero VAD #10 — Wrap whisper.cpp's built-in Silero VAD
• Wrap grammar-constrained decoding #11 — Wrap grammar-constrained decoding
• Test coverage for the translate task (audio → English) #12 — Test coverage for the translate task (audio → English)
• Wrap tinydiarize input control (set_tdrz_enable) #13 — Wrap tinydiarize input control (set_tdrz_enable)
• Wrap lower-level encode/decode entry points #14 — Wrap lower-level encode/decode entry points
• Wrap mid-decode callbacks (progress, new_segment, filter_logits, start_encoder) #15 — Wrap mid-decode callbacks (progress, new_segment, filter_logits, start_encoder)
• Wrap global logging hooks (whisper_set_log_callback) #16 — Wrap global logging hooks (whisper_set_log_callback)
• Wrap buffer-load and custom-loader Context constructors #17 — Wrap buffer-load and custom-loader Context constructors
• Direct beam_search / greedy field accessors on Params #18 — Direct beam_search / greedy field accessors on Params

Already shipped (removed from the list)

• DTW token timestamps — landed in 0.2.0. Enable via ContextParams::with_dtw_token_timestamps(true) + with_dtw_aheads_preset(...); read per-token timing as Token::t_dtw() -> Option<i64>.
• Token-stream iterators — Token-stream iterators: Segment / Token #3, landing in 0.2.1. State::segments_iter() / Segment::tokens_iter() plus the standard adapter trait impls.

[uqio]

DTW token timestamps removed from the omissions list — landed on feat/dtw (PR pending). Safe API:

• ContextParams::with_dtw_token_timestamps(true).with_dtw_aheads_preset(LargeV3Turbo) to enable
• Token::t_dtw() -> Option<i64> to read per-token timing (None = DTW unavailable for this token)
• required_dtw_mem_size_for(preset) to pre-compute the per-preset scratch budget
• All native abort paths inside the DTW helper converted to WhisperError::StateLost via the existing exception shim.

The other items remain deferred — comment on this issue if you have a concrete use case for any of them.