Register AWS Polly as an audio provider with SigV4 request signing,
speech engine discovery, and API-key validation for managed provider
flows.
Add Lemonade as a self-hosted OpenAI-compatible provider, expand
static model discovery to audio registries, and support Azure OpenAI
deployment discovery from resource endpoints.
Sanitize sensitive provider-specific AWS fields in API responses and
update related tests and release notes.
- Stream release: wrap stream body with TransformStream to release
account semaphore only when stream is fully consumed (Thread 1)
- Key scope: remove model from semaphore key — was per-account-per-model,
now truly per-account to match PR motivation (Thread 2)
- Test location: move accountSemaphore.test.ts to tests/unit/ per style guide (Thread 3)
- Fix flaky timestamp assertions in semaphore tests
