fix compiler authoring traps and showcase generation order

packages/syntax/src/tokenizer.ts

@@ -55,6 +55,12 @@ export class Lexer {
     }
   }
 
+  /** True when the next non-trivia characters open a block comment. */
+  startsWithBlockComment(): boolean {
+    this.skipTrivia();
+    return this.src[this.pos] === "/" && this.src[this.pos + 1] === "*";
+  }
+
   /** Read and consume the next structural token. */
   next(): Token {
     this.skipTrivia();