feat(abstractions): add policy evaluation exceptions

Author: rian-be

src/Abstractions/Exceptions/PolicyEvaluationException.cs

@@ -0,0 +1,20 @@
+namespace ModularityKit.Mutator.Abstractions.Exceptions;
+
+/// <summary>
+/// Exception thrown when a policy evaluation fails before producing a decision.
+/// </summary>
+/// <remarks>
+/// Initializes a new instance of <see cref="PolicyEvaluationException"/>.
+/// </remarks>
+/// <param name="policyName">The policy name.</param>
+/// <param name="message">Human-readable description of the failure.</param>
+/// <param name="innerException">The underlying failure.</param>
+public class PolicyEvaluationException(string policyName, string message, Exception? innerException = null)
+    : MutationException(message, innerException ?? new Exception(message))
+{
+
+    /// <summary>
+    /// The name of the policy that failed.
+    /// </summary>
+    public string PolicyName { get; } = policyName;
+}

src/Abstractions/Exceptions/PolicyEvaluationTimeoutException.cs

@@ -0,0 +1,19 @@
+namespace ModularityKit.Mutator.Abstractions.Exceptions;
+
+/// <summary>
+/// Exception thrown when policy evaluation exceeds the configured timeout.
+/// </summary>
+/// <remarks>
+/// Initializes new instance of <see cref="PolicyEvaluationTimeoutException"/>.
+/// </remarks>
+/// <param name="policyName">The policy name.</param>
+/// <param name="timeout">The configured timeout.</param>
+public sealed class PolicyEvaluationTimeoutException(string policyName, TimeSpan timeout) : PolicyEvaluationException(
+        policyName,
+        $"Policy '{policyName}' evaluation timed out after {timeout.TotalSeconds:0.###}s.")
+{
+    /// <summary>
+    /// The configured timeout for policy evaluation.
+    /// </summary>
+    public TimeSpan Timeout { get; } = timeout;
+}