Preserve LLM generation failure metadata

internal/framework/contracts/errors_test.go

@@ -0,0 +1,22 @@
+package contracts
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestLLMGenerationErrorPreservesApplicationMetadata(t *testing.T) {
+	legacy := NewLLMGenerationError(503, "provider failure")
+	if !errors.Is(legacy, ErrLLMGeneration) || legacy.StatusCode() != 503 || legacy.FailureKind() != LLMGenerationFailureGeneration || legacy.RetriesExhausted() || legacy.Attempts() != 0 {
+		t.Fatalf("legacy generation error = %#v", legacy)
+	}
+
+	err := NewLLMGenerationErrorWithMetadata(429, "provider failure", LLMGenerationMetadata{
+		FailureKind:      LLMGenerationFailureProviderStatus,
+		RetriesExhausted: true,
+		Attempts:         3,
+	})
+	if !errors.Is(err, ErrLLMGeneration) || err.StatusCode() != 429 || err.FailureKind() != LLMGenerationFailureProviderStatus || !err.RetriesExhausted() || err.Attempts() != 3 {
+		t.Fatalf("generation error = %#v", err)
+	}
+}