Adds 'speech-sdk' as a fifth built-in TTS provider backed by @speech-sdk/core
(Apache 2.0). Models use the provider/model format; requests go from the
server directly to the provider's API with the user's own key. Existing
providers, defaults, and config are untouched.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Remove fallbackProviderRef usage from settings and config context to streamline
provider resolution. Adjust normalizeLegacyProviderRef to retain 'default-openai'
unless a non-default fallback is explicitly provided. Update provider listing to
enforce deterministic ordering by updatedAt, createdAt, and slug. Expand unit tests
to verify provider ordering, legacy ref normalization, and selection logic.
Transition all TTS-related logic, types, and UI to use the new providerRef/providerType model in place of legacy ttsProvider fields. Introduce a centralized tts-provider-policy module to encapsulate provider/model capability checks, default value resolution, and compatibility logic. Update all API routes, contexts, hooks, components, and tests to use providerRef and providerType, ensuring consistent handling of built-in and shared TTS providers. Remove legacy defaultTtsModel config in favor of per-provider defaults and shared provider admin control. Add the showAllProviderModels runtime flag to restrict users to provider default models when desired.
BREAKING CHANGE: ttsProvider fields are replaced by providerRef/providerType throughout the codebase; defaultTtsModel config is removed in favor of per-provider defaults.
