Add Qwen Audio 3 milestone two controls - #5

Summary

Milestone 2 implementation and bounded authorized evaluation for Qwen-Audio-3:

• add backward-compatible Standard, Low-latency dictation, Long-form, and Custom recognition presets
• add documented multi_threshold_mode_enabled and optional speech_noise_threshold controls
• parse bounded sentence/timed-unit metadata without changing transcript assembly
• advance safe aggregate diagnostics to schema 4
• add Regional/Custom endpoint routing for Beijing and Singapore
• add optional hostname-based Workspace ID routing with transport-safe validation
• preserve legacy/custom endpoints and keep endpoint, Workspace ID, models, credentials, transcript, and timed-unit text out of diagnostics

Evaluation

• 17 fixed private WAV files replayed under three presets: 51/51 Streaming requests succeeded
• all tested 250–2200 ms inserted-digital-silence samples retained both clauses
• 15/15 speech files produced output under every preset; silence/noise-only false positives were 0/2 under every preset
• one realtime session per preset completed; 73 timestamp-bearing results and 106 timed units were accepted with zero rejected/truncated units
• one live cancellation canary produced no output
• Beijing Regional empty-workspace Streaming and Native canaries succeeded
• no corpus audio, references, transcripts, provider messages, credentials, endpoints, Workspace IDs, or raw diagnostics are committed

See docs/qwen-audio3-milestone2-evaluation.md for aggregate results and limits.

Scope boundaries

• no timestamp identity-based deduplication or correction replacement
• no reconnect/replay or retained Audio3 audio
• no context collection or Filetrans
• no automatic credential-region probing
• no claim of Singapore feature parity or workspace-route success; those routes were not attempted without matching scoped credentials
• Standard remains the default; bounded one-speaker results are not general accuracy or latency recommendations

Validation

• cargo fmt --all -- --check
• cargo check --locked --all-targets
• cargo test --locked --all-targets — 241 passed
• cargo clippy --locked --all-targets -- -D warnings
• make validate-qml
• git diff --check