feat[api]: add Sortformer v2.1 + AOSC streaming diarization support

[pratiknarola-t]

Bumps @qvac/transcription-parakeet 0.4.0 -> 0.5.0 (MINOR -- additive
API only; no breaking changes).

🎯 What problem does this PR solve?

• v1 Sortformer streaming uses a fixed-size sliding-history window; once
  a speaker goes silent long enough to roll out of the window, their
  slot identity drifts onto a different physical voice when they return.
• Continuous single-speaker stretches collapse all voices onto
  sortformer_0 once two speakers have been seen, breaking live
  speaker-tagged transcripts.
• v2.1 + AOSC (Audio-Online Speaker Cache, NeMo-ported) fixes this in
  parakeet-cpp, but until now there was no way to consume it from the
  JS layer.

📝 How does it solve it?

• Bump parakeet-cpp to version>= 2026-05-20 (the qvac-registry-vcpkg
  bump in PR chore(qvac-sdk): Remove bundler and cli from sdk #156 pulls in PRs update version #22 / testing qvac-lib-error-base-workflow #24 of qvac-ext-lib-whisper.cpp).
• Plumb 6 AOSC knobs (streamingSpkCacheEnable, streamingSpkCacheLen,
  streamingFifoLen, streamingChunkLeftContextMs,
  streamingChunkRightContextMs, streamingSpkCacheUpdatePeriod) from
  JS through ParakeetConfig -> ParakeetModel /
  ParakeetStreamingProcessor -> parakeet::SortformerStreamingOptions,
  for both the in-process Mode-3 streaming path and the duplex
  runStreaming() processor.
• v2.1 is auto-detected by the engine via the GGUF metadata tag
  parakeet.model_variant; AOSC defaults mirror parakeet-cpp's
  NeMo-port tuning (188 / 188 / 80 / 560 / 144, enabled).
• Defaults: v2.1 becomes the streaming Sortformer; v1 stays the offline
  default. Both GGUFs remain registered.
• New examples/live-mic-diarized-aosc.js exposes every AOSC knob as a
  CLI flag for A/B comparison against the v1 sliding-window path.

🧪 How was it tested?

• Built locally against a vcpkg overlay pointing at the PR chore(qvac-sdk): Remove bundler and cli from sdk #156 branch;
  addon compiled cleanly with all 6 new AOSC field references through
  ParakeetStreamingProcessor.cpp, ParakeetModel.cpp, AddonJs.hpp,
  and JSAdapter.cpp.
• Full integration suite: 37/37 tests pass, 72/72 assertions in 145s
  (macOS arm64, all q8_0 GGUFs staged including v2.1 Sortformer).
• New test/integration/sortformer-aosc-streaming.test.js covers
  default-AOSC streaming + streamingSpkCacheEnable=false fallback to
  the v1 sliding-window code path. Confirmed via engine logs that the
  override actually disables the cache (Sortformer AOSC enabled line
  only prints when AOSC is active).
• v1 Sortformer desktop integration + GPU smoke tests still pass -- no
  regression to the existing diarization path.

🔌 API Changes

New optional fields on ParakeetConfig, mirrored as per-call overrides
on StreamingRunConfig. All default to parakeet-cpp's NeMo-port
tuning; specifying them is opt-in. Ignored on v1 / v2 Sortformer and on
non-Sortformer engines (no-op forwarding is safe).

import { TranscriptionParakeet } from "@qvac/transcription-parakeet";

const model = new TranscriptionParakeet({
  files: { model: "diar_streaming_sortformer_4spk-v2.1.q8_0.gguf" },
  config: {
    parakeetConfig: {
      streaming: true,
      streamingChunkMs: 2000,
      // AOSC (v2.1+ only; auto-detected via GGUF metadata)
      streamingSpkCacheEnable: true,         // default
      streamingSpkCacheLen: 188,             // long-term cache rows
      streamingFifoLen: 188,                 // warmup FIFO rows
      streamingChunkLeftContextMs: 80,       // ~1 encoder frame
      streamingChunkRightContextMs: 560,     // ~7 encoder frames
      streamingSpkCacheUpdatePeriod: 144,    // FIFO-overflow pop count
    },
  },
});

Depends on

• qvac-registry-vcpkg chore(qvac-sdk): Remove bundler and cli from sdk #156 (parakeet-cpp 2026-05-20 bump). CI will not
  resolve the new version>= constraint until that PR merges.
• Separate registry-server PR for the v2.1 GGUF entry in
  models.prod.json (out of scope for this PR -- handled independently).
• Upload of diar_streaming_sortformer_4spk-v2.1.q8_0.gguf to S3 (the
  GGUF the new test resolves via MODEL_CONFIGS.sortformerStreaming).

Follow-up (separate PR, not in scope here)

SDK adoption (@qvac/sdk schema + plugin + example) lands in a
separate PR after this addon is published and the v2.1 GGUF entry has
synced into sdk/models/registry/models.ts. The SDK needs both pieces
in place before its schema can meaningfully forward AOSC knobs.

[ishanvohra2]

The SDK changes should only occur after the parakeet package is published.
You can split this into two PRs. The second PR can target SDK changes and the version update for parakeet.
@pratiknarola-t

[github-actions]

Tier-based Approval Status

**PR Tier:** TIER1

**Current Status:** ✅ APPROVED

**Requirements:**
- 1 Team Member approval ✅ (1/1)
- 1 Team Lead OR Management approval ✅ (1/1)



---
*This comment is automatically updated when reviews change.*

[GustavoA1604]

1. Update setup-models flow to also fetch and convert sortformer 2.1 model (update all necessary scripts)
2. Add new entry in CHANGELOG.md under [Unreleased] with what is being added in this PR

[GustavoA1604]

Final on-pr run here