feat(agents): enforce one librarian timeout budget

- add LIBRARIAN_TIMEOUT config (default 180s) and enforce it with
  asyncio.wait_for inside delegate_to_librarian, covering the live
  paths (steward direct delegation and SSE streaming) that had no cap
- timeouts fail honestly: success=False with a curated butler sentence,
  detail in logs
- set an explicit timeout on TatlockOllamaProvider's AsyncOpenAI client
  from OLLAMA_TIMEOUT instead of the SDK default (~600s per LLM call)
- remove the contradictory unused 60s default from
  AgentRequest.timeout_seconds; coordination falls back to the
  configured budget

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/core/config.py

@@ -42,7 +42,7 @@ class Environment(str, Enum):
 class Config(BaseSettings):
     """
     Global application configuration.
-    
+
     Loads from environment variables and .env file.
     Domain-specific configs should be in their respective modules.
     """
@@ -52,18 +52,18 @@ class Config(BaseSettings):
         case_sensitive=True,
         extra="ignore",
     )
-    
+
     # Application
     APP_NAME: str = "OpenAI-Compatible API"
     APP_VERSION: str = Field(default_factory=_get_version_from_pyproject)
     ENVIRONMENT: Environment = Environment.DEVELOPMENT
     DEBUG: bool = Field(default=False, description="Debug mode")
-    
+
     # API Configuration
     API_HOST: str = Field(default="0.0.0.0", description="API host")
     API_PORT: int = Field(default=8000, description="API port")
     API_PREFIX: str = Field(default="/v1", description="API route prefix")
-    
+
     # Anthropic Configuration (Claude - cloud fallback)
     ANTHROPIC_API_KEY: str | None = Field(
         default=None,
@@ -125,6 +125,10 @@ class Config(BaseSettings):
     )
 
     # Library-Desk Configuration (The Librarian backend)
+    LIBRARIAN_TIMEOUT: int = Field(
+        default=180,
+        description="Total time budget for a librarian delegation in seconds"
+    )
     LIBRARY_DESK_HOST: HttpUrl = Field(
         default="http://localhost:8089",
         description="Library-Desk API URL"
@@ -259,7 +263,7 @@ class Config(BaseSettings):
 def get_config() -> Config:
     """
     Get cached configuration instance.
-    
+
     Uses lru_cache to ensure config is loaded once and reused.
     """
     return Config()