fix(scripts): read check-osv-exemptions selfTest() before destructuring it

The handshake was placed after `const { passed, lines } = selfTest()`, so an
early return made the destructuring throw a TypeError before the check could
run — the very accident that made this gate read HELD without a handshake. The
census now reports the named refusal instead of a stack trace.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LAwHpn4uVuf4N1geBcD5i3

Author: claude

scripts/check-osv-exemptions.mjs

@@ -500,7 +500,10 @@ function selfTest() {
 
 function main() {
   if (process.argv.includes('--self-test')) {
-    const { passed, lines } = selfTest();
+    // Read BEFORE destructuring: an early return yields `undefined`, and
+    // destructuring that throws a TypeError before the handshake is reached —
+    // an accidental non-zero exit is not a verdict handshake (#13798).
+    const selfTestResult = selfTest();
     if (!selfTestReachedVerdict) {
       console.error(
         '\n✗ check-osv-exemptions self-test: selfTest() returned without reaching its verdict,\n'
@@ -509,6 +512,7 @@ function main() {
       );
       process.exit(1);
     }
+    const { passed, lines } = selfTestResult;
     console.log('check-osv-exemptions self-test (both directions):');
     for (const line of lines) console.log(line);
     if (!passed) {