Fix invalid inline-checks doc examples; document missing-score fail-safe

Address review:
- The XML doc examples used invalid SDK enum values (PROMPT_ATTACK, US_SSN)
  that would fail-closed on every call if copied. Use real constants
  (JAILBREAK/PROMPT_INJECTION/PROMPT_LEAKAGE; US_SOCIAL_SECURITY_NUMBER/EMAIL/PHONE).
- Expand the comment on ChecksTripped's missing-score handling to make the
  deliberate fail-safe (deny) trade-off explicit.

Author: GarrettBeatty

src/AWS.Bedrock.MAG/Internal/GuardrailResponseMapper.cs

@@ -101,7 +101,10 @@ public static bool ChecksTripped(
             return tripped.Count > 0;
         }
 
-        // A finding with no score is treated as meeting the threshold (fail-safe toward deny).
+        // A finding with no score is treated as meeting the threshold. This is deliberate: an entry only
+        // appears in the results when the guardrail flagged something, so a missing score denies (fail-safe)
+        // rather than risk letting a real detection through. The trade-off is possible over-blocking if the
+        // API ever returns a flagged entry without a score.
         private static bool Meets(double? score, double threshold) => !score.HasValue || score.Value >= threshold;
     }
 }

src/AWS.Bedrock.MAG/Policy/GuardrailChecksOptions.cs

@@ -15,10 +15,10 @@ public sealed class GuardrailChecksOptions
         /// <summary>Content-filter categories to evaluate (e.g. HATE, INSULTS, SEXUAL, VIOLENCE, MISCONDUCT).</summary>
         public IList<string> ContentFilterCategories { get; } = new List<string>();
 
-        /// <summary>Prompt-attack categories to evaluate (e.g. PROMPT_ATTACK).</summary>
+        /// <summary>Prompt-attack categories to evaluate (e.g. JAILBREAK, PROMPT_INJECTION, PROMPT_LEAKAGE).</summary>
         public IList<string> PromptAttackCategories { get; } = new List<string>();
 
-        /// <summary>PII entity types to detect (e.g. US_SSN, EMAIL, NAME).</summary>
+        /// <summary>PII entity types to detect (e.g. US_SOCIAL_SECURITY_NUMBER, EMAIL, PHONE).</summary>
         public IList<string> SensitiveInformationEntities { get; } = new List<string>();
 
         /// <summary>