Pin temporalio to 1.15.0 as plugins API is still experimental (#2582)

Author: DouweM

pydantic_ai_slim/pyproject.toml

@@ -94,7 +94,7 @@ ag-ui = ["ag-ui-protocol>=0.1.8", "starlette>=0.45.3"]
 # Retries
 retries = ["tenacity>=8.2.3"]
 # Temporal
-temporal = ["temporalio>=1.15.0"]
+temporal = ["temporalio==1.15.0"]
 
 [tool.hatch.metadata]
 allow-direct-references = true