fix: drop empty text nodes left behind by whitespace stripping

After strip flags trim surrounding whitespace, TextNodes whose chars
become empty would still appear in the body as spurious append calls
in the wire format. Remove them in a second pass after stripping.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: NullVoxPopuli

packages/@glimmer/syntax/lib/parser/tokenizer-event-handlers.ts

@@ -344,6 +344,14 @@ function stripBodyWhitespace(body: Stripable[]): void {
       }
     }
   }
+
+  // Drop any text nodes that are now empty after stripping.
+  for (let i = body.length - 1; i >= 0; i--) {
+    const stmt = body[i]!;
+    if (stmt.type === 'TextNode' && stmt.chars === '') {
+      body.splice(i, 1);
+    }
+  }
 }
 
 function getOpenStrip(stmt: Stripable): boolean {