v0.40.0

Tampering swapped the token's last character for a fixed one. Whenever the
freshly minted token already ended in it the token was unchanged and
authenticated, so the test failed at random (CI run 37511248743). The final
base64url character carries only a few significant bits, which makes that much
likelier than 1 in 64. Pick a replacement that differs from the original.

Co-Authored-By: Claude Opus 5.5 (1M context) noreply@anthropic.com