Address code review feedback: Fix comments and error messages

Co-authored-by: TomeHirata <[email protected]>

Author: Copilot

dspy/predict/react.py

@@ -155,12 +155,12 @@ def _call_with_potential_trajectory_truncation(self, module, trajectory, **input
                 try:
                     trajectory = self.truncate_trajectory(trajectory)
                 except ValueError:
-                    # Cannot truncate further, re-raise as a clear error
+                    # Cannot truncate further, raise a clear error
                     raise ValueError(
                         "The context window was exceeded and the trajectory could not be truncated further."
-                    )
+                    ) from None
         raise ValueError(
-            "The context window was exceeded after 3 attempts to truncate the trajectory."
+            "The context window was exceeded even after 3 attempts to truncate the trajectory."
         )
 
     async def _async_call_with_potential_trajectory_truncation(self, module, trajectory, **input_args):
@@ -175,12 +175,12 @@ async def _async_call_with_potential_trajectory_truncation(self, module, traject
                 try:
                     trajectory = self.truncate_trajectory(trajectory)
                 except ValueError:
-                    # Cannot truncate further, re-raise as a clear error
+                    # Cannot truncate further, raise a clear error
                     raise ValueError(
                         "The context window was exceeded and the trajectory could not be truncated further."
-                    )
+                    ) from None
         raise ValueError(
-            "The context window was exceeded after 3 attempts to truncate the trajectory."
+            "The context window was exceeded even after 3 attempts to truncate the trajectory."
         )
 
     def truncate_trajectory(self, trajectory):