Skip empty statements in parser and test infrastructure

- Parser: Skip leading semicolons in ParseStatements to handle empty
  statements (just ';') gracefully
- Test: Skip empty semicolon statements in splitStatements to match
  ClickHouse behavior which doesn't count empty statements

This fixes the statement numbering mismatch that caused
03036_join_filter_push_down_equivalent_sets to fail, and also
fixes 02155_multiple_inserts_for_formats_with_suffix.

Author: claude

parser/parser.go

@@ -89,6 +89,14 @@ func (p *Parser) ParseStatements(ctx context.Context) ([]ast.Statement, error) {
 		default:
 		}
 
+		// Skip leading semicolons (empty statements)
+		for p.currentIs(token.SEMICOLON) {
+			p.nextToken()
+		}
+		if p.currentIs(token.EOF) {
+			break
+		}
+
 		stmt := p.parseStatement()
 		if stmt != nil {
 			statements = append(statements, stmt)

parser/parser_test.go

@@ -58,7 +58,8 @@ func splitStatements(content string) []string {
 		// Check if statement is complete (ends with ;)
 		if strings.HasSuffix(trimmed, ";") {
 			stmt := strings.TrimSpace(current.String())
-			if stmt != "" {
+			// Skip empty statements (just semicolons or empty)
+			if stmt != "" && stmt != ";" {
 				statements = append(statements, stmt)
 			}
 			current.Reset()

parser/testdata/02155_multiple_inserts_for_formats_with_suffix/metadata.json

@@ -1,13 +1 @@
-{
-  "explain_todo": {
-    "stmt22": true,
-    "stmt23": true,
-    "stmt24": true,
-    "stmt25": true,
-    "stmt26": true,
-    "stmt27": true,
-    "stmt28": true,
-    "stmt29": true,
-    "stmt30": true
-  }
-}
+{}

parser/testdata/03036_join_filter_push_down_equivalent_sets/metadata.json

@@ -1,39 +1 @@
-{
-  "explain_todo": {
-    "stmt15": true,
-    "stmt16": true,
-    "stmt17": true,
-    "stmt18": true,
-    "stmt19": true,
-    "stmt20": true,
-    "stmt21": true,
-    "stmt22": true,
-    "stmt23": true,
-    "stmt24": true,
-    "stmt25": true,
-    "stmt26": true,
-    "stmt27": true,
-    "stmt28": true,
-    "stmt29": true,
-    "stmt30": true,
-    "stmt31": true,
-    "stmt32": true,
-    "stmt33": true,
-    "stmt34": true,
-    "stmt35": true,
-    "stmt36": true,
-    "stmt37": true,
-    "stmt38": true,
-    "stmt39": true,
-    "stmt40": true,
-    "stmt41": true,
-    "stmt42": true,
-    "stmt43": true,
-    "stmt44": true,
-    "stmt45": true,
-    "stmt46": true,
-    "stmt47": true,
-    "stmt48": true,
-    "stmt49": true
-  }
-}
+{}