Add automatic validation system for Score results

plexus/docs/score-yaml-format.md

@@ -310,11 +310,67 @@ data:
   balance: false  # Whether to balance positive/negative examples
 ```
 
+## Validation
+
+Validation rules throw exceptions if score results don't match expected formats.
+
+```yaml
+validation:
+  value:
+    valid_classes: ["Yes", "No", "Maybe"]           # Must be one of these (case-insensitive by default)
+    patterns: ["^NQ - (?!Other$).*"]                # Must match regex (NQ- anything except "Other")
+    minimum_length: 1                               # Min string length
+    maximum_length: 50                              # Max string length
+    case_sensitive: false                           # Case-insensitive comparison (default: false)
+  explanation:
+    minimum_length: 10
+    patterns: [".*evidence.*", ".*found.*"]         # Must contain "evidence" or "found"
+```
+
+**All constraints must pass (AND logic). Validation runs automatically in `predict()`.**
+
+### Case Sensitivity
+
+By default, `valid_classes` comparisons are **case-insensitive** for convenience:
+
+```yaml
+validation:
+  value:
+    valid_classes: ["Yes", "No"]  # Matches "yes", "YES", "Yes", "no", "NO", "No"
+```
+
+Enable case-sensitive comparison when exact case matters:
+
+```yaml
+validation:
+  value:
+    valid_classes: ["Yes", "No"]
+    case_sensitive: true  # Only matches exact case: "Yes", "No"
+```
+
+```yaml
+# Simple cases
+validation:
+  value:
+    valid_classes: ["Yes", "No"]
+
+validation:
+  value:
+    patterns: ["^Critical - .*"]
+
+# Mixed validation - value must be in list AND match pattern
+validation:
+  value:
+    valid_classes: ["Yes", "No", "NQ - Pricing"] 
+    patterns: ["^(Yes|No)$", "^NQ - (?!Other$).*"]
+```
+
 ## Best Practices
 
 1. Use modern `Classifier` over legacy classifier types
 2. Structure graphs to handle early termination with conditions
 3. Use descriptive node names and field mappings
 4. Leverage slicers for complex transcript analysis
 5. Include clear system and user prompts
-6. Avoid redundant processing by sharing results between nodes 
+6. Avoid redundant processing by sharing results between nodes
+7. Add validation constraints to ensure consistent score outputs