test(launch-probe): say the /bin/bash parse case discriminates only on macOS

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

test/gstack-launch-probe.test.ts

@@ -83,8 +83,9 @@ describe.skipIf(process.platform === 'win32')('gstack-launch-probe.sh classifica
   });
 
   // Value: protects=the probe parses under macOS /bin/bash 3.2, so gstack-doctor can source it (#3601);
-  //   fails_when=a case pattern inside $( ) loses its leading (; why_new=the cases above run PATH bash, 5.x on Linux CI; seam=none
-  test.skipIf(!fs.existsSync('/bin/bash'))('parses under /bin/bash (bash 3.2 on macOS)', () => {
+  //   fails_when=a case pattern inside $( ) loses its leading (, on a macOS runner only: Linux /bin/bash is 5.x, which parsed the old line,
+  //   so test/bash32-case-in-substitution.test.ts is the Linux CI guard; why_new=the cases above run PATH bash; seam=none
+  test.skipIf(!fs.existsSync('/bin/bash'))('parses under /bin/bash (catches #3601 only where /bin/bash is 3.2, i.e. macOS)', () => {
     const r = spawnSync('/bin/bash', ['-n', PROBE], { encoding: 'utf8', timeout: 30_000 });
     expect(r.stderr).toBe('');
     expect(r.status).toBe(0);