Zhipu's `data.limits[]` returns 1 entry for legacy plans (subscribed
before 2026-02-12) and 2 entries for current plans. Previously every
TOKENS_LIMIT entry was hardcoded as `five_hour`, so the weekly bucket
was rendered with the 5-hour i18n label.
Sort TOKENS_LIMIT entries by nextResetTime ascending and assign
`five_hour` to index 0, `weekly_limit` to index 1. Legacy plans
naturally degrade to a single five_hour tier.
Also harden the parser: case-insensitive type match (defends against
upstream casing changes), reuse TIER_FIVE_HOUR/TIER_WEEKLY_LIMIT
constants, and add 8 unit tests covering both plan shapes plus
defensive edge cases.