GLM quota parsing only accepted TOKENS_LIMIT and wrote every limit to a
single "session" key, so credit-based plans showed nothing and later
intervals overwrote earlier ones. Accept CREDIT_LIMIT too and derive the
quota key from the limit unit (5h session, 7d weekly, tokens, custom).
Moves the parser into its own usage/glm.js, re-exported from misc.js.
fcfcced4ab