refactor: collapse TTS vendor configs; add resolved_sample_rate accessor

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: plutoless

src/agora_agent/agentkit/agent.py

@@ -473,7 +473,7 @@ def with_llm(self, vendor: BaseLLM) -> "Agent":
         return new_agent
 
     def with_tts(self, vendor: BaseTTS) -> "Agent":
-        sample_rate = vendor.sample_rate
+        sample_rate = vendor.resolved_sample_rate
         if (
             self._avatar_required_sample_rate not in (None, 0)
             and sample_rate is not None

src/agora_agent/agentkit/vendors/base.py

@@ -28,26 +28,26 @@ def to_config(self) -> Dict[str, Any]:
         """Serialize the LLM configuration to a dict for the REST API."""
 
 
-class BaseTTS(ABC):
+class BaseTTS(BaseModel, ABC):
     """Abstract base class for all TTS vendor implementations.
 
-    Subclasses must implement :meth:`to_config` and :attr:`sample_rate`.
+    Subclasses must implement :meth:`to_config`.
 
-    ``sample_rate`` is used by :class:`~agora_agent.agentkit.AgentSession` to
-    validate TTS/avatar compatibility at runtime (avatars require a specific
-    sample rate).  Subclasses should return ``None`` when the user has not
-    explicitly configured a sample rate, which will cause a warning at session
-    start time rather than a hard error.
+    :attr:`resolved_sample_rate` is used by
+    :class:`~agora_agent.agentkit.AgentSession` to validate TTS/avatar
+    compatibility at runtime (avatars require a specific sample rate).  It
+    returns ``None`` when the user has not explicitly configured a sample rate,
+    which will cause a warning at session start time rather than a hard error.
     """
 
     @abstractmethod
     def to_config(self) -> Dict[str, Any]:
         """Serialize the TTS configuration to a dict for the REST API."""
 
     @property
-    @abstractmethod
-    def sample_rate(self) -> Optional[int]:
-        """The configured sample rate in Hz, or ``None`` if not explicitly set."""
+    def resolved_sample_rate(self) -> Optional[int]:
+        """The effective configured sample rate in Hz, or None if not set."""
+        return getattr(self, "sample_rate", None)
 
 
 class BaseSTT(BaseModel, ABC):