Add nested paren table ref handling and VariableTableReference alias marshaling

- Handle nested parentheses in FROM clause that contain derived tables with
  aliases and JOINs (e.g., ((SELECT ...) AS t10 INNER JOIN ...))
- Add Alias field marshaling for VariableTableReference in tableReferenceToJSON
- Add support for bracketed identifiers as aliases for VariableTableReference
- Enables BaselinesCommon_FromClauseTests

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

ast/table_reference.go

@@ -5,3 +5,11 @@ type TableReference interface {
 	Node
 	tableReference()
 }
+
+// OdbcQualifiedJoinTableReference represents an ODBC qualified join syntax: { OJ ... }
+type OdbcQualifiedJoinTableReference struct {
+	TableReference TableReference
+}
+
+func (o *OdbcQualifiedJoinTableReference) node()           {}
+func (o *OdbcQualifiedJoinTableReference) tableReference() {}

parser/marshal.go

@@ -2785,13 +2785,24 @@ func tableReferenceToJSON(ref ast.TableReference) jsonNode {
 			node["Join"] = tableReferenceToJSON(r.Join)
 		}
 		return node
+	case *ast.OdbcQualifiedJoinTableReference:
+		node := jsonNode{
+			"$type": "OdbcQualifiedJoinTableReference",
+		}
+		if r.TableReference != nil {
+			node["TableReference"] = tableReferenceToJSON(r.TableReference)
+		}
+		return node
 	case *ast.VariableTableReference:
 		node := jsonNode{
 			"$type": "VariableTableReference",
 		}
 		if r.Variable != nil {
 			node["Variable"] = scalarExpressionToJSON(r.Variable)
 		}
+		if r.Alias != nil {
+			node["Alias"] = identifierToJSON(r.Alias)
+		}
 		node["ForPath"] = r.ForPath
 		return node
 	case *ast.VariableMethodCallTableReference: