Decodes a JWT without trusting it and lints the header and claims: alg none, remote jku/x5u keys, missing or expired exp, nbf/iat clock skew, millisecond timestamps, long lifetimes, iss/aud mismatches, sensitive data in the payload, and HMAC signature checks with a secret from an env var. Use when a login or API call fails with 401, or when reviewing token settings. Includes a stdlib Python inspector with --self-test.
