Fix code review issues: simplify chi-square calculation and add p-value bounds check

Co-authored-by: EdgeTypE <34396598+EdgeTypE@users.noreply.github.com>

Author: Copilot

patternanalyzer/plugins/chi_square.py

@@ -55,7 +55,7 @@ def run(self, data: BytesView, params: dict) -> TestResult:
         observed_bytes = len(counter)
         missing_bytes = 256 - observed_bytes
         if missing_bytes > 0:
-            chi_square += missing_bytes * (expected ** 2 / expected)
+            chi_square += missing_bytes * expected
 
         # Degrees of freedom = 256 - 1 = 255
         df = 255
@@ -116,7 +116,7 @@ def finalize(self, params: dict) -> TestResult:
         observed_bytes = len(counter)
         missing_bytes = 256 - observed_bytes
         if missing_bytes > 0:
-            chi_square += missing_bytes * (expected ** 2 / expected)
+            chi_square += missing_bytes * expected
 
         # Degrees of freedom = 256 - 1 = 255
         df = 255

patternanalyzer/plugins/permutation_test.py

@@ -93,6 +93,9 @@ def run(self, data: BytesView, params: dict) -> TestResult:
         # Calculate p-value
         p_value = 1.0 - self._chi_square_cdf(chi_square, df)
 
+        # Ensure p_value is in valid range [0, 1]
+        p_value = max(0.0, min(1.0, p_value))
+        
         # Determine if test passed
         alpha = float(params.get("alpha", 0.01))
         passed = p_value > alpha