Fix Issue 1: Make Trajectory None guards thorough (matching SRE patch quality)

purpose_agent/types.py

@@ -3,6 +3,10 @@ Core data types for the Purpose Agent framework.
 
 All modules exchange these types — this keeps the architecture modular
 and lets you swap out any component without touching the others.
+
+NOTE: sre_patches.py monkey-patches Trajectory properties at import time
+with even more robust None guards. The versions here are the baseline;
+SRE patches are the authoritative runtime versions.
 """
 
 from __future__ import annotations
@@ -105,6 +109,9 @@ class Trajectory:
     
     The Experience Replay module stores these and the Optimizer extracts
     heuristics from high-reward trajectories.
+    
+    NOTE: sre_patches.py replaces these properties with more thorough None guards.
+    The patched versions check both `s.score is not None` AND `s.score.delta is not None`.
     """
     task_description: str
     purpose: str
@@ -114,30 +121,33 @@ class Trajectory:
 
     @property
     def cumulative_reward(self) -> float:
-        """Sum of all positive deltas in the trajectory."""
-        return sum(
-            s.score.delta for s in self.steps
-            if s.score is not None and s.score.delta > 0
-        )
+        """Sum of all positive deltas in the trajectory (None-safe)."""
+        total = 0.0
+        for s in self.steps:
+            if s.score is not None and s.score.delta is not None and s.score.delta > 0:
+                total += s.score.delta
+        return total
 
     @property
     def total_delta(self) -> float:
-        """Net state improvement across the entire trajectory."""
-        return sum(
-            s.score.delta for s in self.steps if s.score is not None
-        )
+        """Net state improvement across the entire trajectory (None-safe)."""
+        total = 0.0
+        for s in self.steps:
+            if s.score is not None and s.score.delta is not None:
+                total += s.score.delta
+        return total
 
     @property
     def success_rate(self) -> float:
-        """Fraction of steps that improved state."""
-        scored = [s for s in self.steps if s.score is not None]
+        """Fraction of steps that improved state (None-safe)."""
+        scored = [s for s in self.steps if s.score is not None and s.score.delta is not None]
         if not scored:
             return 0.0
         return sum(1 for s in scored if s.score.improved) / len(scored)
 
     @property
     def final_phi(self) -> float | None:
-        """Final Φ value (state-distance-to-goal) at end of trajectory."""
+        """Final Φ value (state-distance-to-goal) at end of trajectory (None-safe)."""
         scored = [s for s in self.steps if s.score is not None]
         if not scored:
             return None