Fix Identifier handling in FormatDataType and escape strings in CAST explain

- Add Identifier handling in FormatDataType to properly format
  AggregateFunction types that contain function name identifiers
- Escape string literals in CAST explain output to properly handle
  null bytes and other control characters

Tests fixed:
- 02688_aggregate_states (all statements)
- 02477_single_value_data_string_regression
- 02689_meaningless_data_types
- 02731_nothing_deserialization
- 02885_arg_min_max_combinator
- 03011_definitive_guide_to_cast
- 03210_variant_with_aggregate_function_type
- 03254_normalize_aggregate_states_with_named_tuple_args
- 03411_iceberg_bucket

Author: claude

internal/explain/format.go

@@ -286,6 +286,9 @@ func FormatDataType(dt *ast.DataType) string {
 			} else {
 				params = append(params, fmt.Sprintf("%v", p))
 			}
+		} else if ident, ok := p.(*ast.Identifier); ok {
+			// Identifier (e.g., function name in AggregateFunction types)
+			params = append(params, ident.Name())
 		} else {
 			params = append(params, fmt.Sprintf("%v", p))
 		}

internal/explain/functions.go

@@ -489,8 +489,11 @@ func explainCastExprWithAlias(sb *strings.Builder, n *ast.CastExpr, alias string
 				// NULL stays as Literal NULL, not formatted as a string
 				fmt.Fprintf(sb, "%s  Literal NULL\n", indent)
 			} else {
-				// Simple literal - format as string
+				// Simple literal - format as string (escape special chars for string literals)
 				exprStr := formatExprAsString(lit)
+				if lit.Type == ast.LiteralString {
+					exprStr = escapeStringLiteral(exprStr)
+				}
 				fmt.Fprintf(sb, "%s  Literal \\'%s\\'\n", indent, exprStr)
 			}
 		} else if negatedLit := extractNegatedLiteral(n.Expr); negatedLit != "" {

parser/testdata/02477_single_value_data_string_regression/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt12": true,
-    "stmt4": true,
-    "stmt8": true
-  }
-}
+{}

parser/testdata/02688_aggregate_states/metadata.json

@@ -1,11 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true,
-    "stmt2": true,
-    "stmt3": true,
-    "stmt4": true,
-    "stmt5": true,
-    "stmt6": true,
-    "stmt7": true
-  }
-}
+{}

parser/testdata/02689_meaningless_data_types/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true,
-    "stmt2": true
-  }
-}
+{}

parser/testdata/02731_nothing_deserialization/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true
-  }
-}
+{}

parser/testdata/02885_arg_min_max_combinator/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt6": true
-  }
-}
+{}

parser/testdata/03011_definitive_guide_to_cast/metadata.json

@@ -1,7 +1,6 @@
 {
   "explain_todo": {
     "stmt36": true,
-    "stmt53": true,
-    "stmt84": true
+    "stmt53": true
   }
 }

parser/testdata/03210_variant_with_aggregate_function_type/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt4": true,
-    "stmt7": true
+    "stmt4": true
   }
 }

parser/testdata/03254_normalize_aggregate_states_with_named_tuple_args/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}