Upgrade qwentts.cpp to September 28 revision and ABI v5

[andimarafioti]

The previous native pin is from July 17 and uses ABI v2; current qwentts.cpp requires ABI v5. Pin all wheel workflows and the runtime identity guard to upstream master 6fae92914045cd83364d2845ceaa0f7969727319 (September 28, 2026) and match both parameter structs to its header.

Preserve Python sampling flags by translating greedy decoding to zero temperature. Move buffered codec_chunk_sec to context initialization, remove obsolete codec_left_context_sec, and expose model/language queries. Contexts continue to serialize requests with native max_batch=1. Document the API migration and update the build compatibility patches for the moved Metal shader and upstream logging changes, preserving missing-tokenizer errors.

Validation:

• 85 tests pass against the freshly built Metal library, including every ctypes struct size/field offset, native defaults, old-library rejection, and sampling translation.
• Real Metal streaming synthesis with local Base Q8_0 weights produces five chunks / 2.08 seconds of finite, non-silent PCM.
• Buffered greedy synthesis with a 0.64-second codec chunk, model/language queries, cancellation, and subsequent context reuse pass on Metal.
• An arm64 wheel builds, repairs with delocate, passes strict twine checks, and loads its bundled ABI v5 library from an isolated installed location.
• All four workflow files parse and use the same pin; source patches restore the upstream checkout after building.

Version metadata is unchanged. No generated libraries, wheels, or build artifacts are committed. Linux CUDA builds remain to be validated through their normal workflows.