Fix z.ai MCP monthly window label

[ThiagoCAltoe]

Summary

• show z.ai MCP TIME_LIMIT usage as Monthly instead of the raw 1 minute window API label
• keep token limit window labels unchanged
• add regression coverage for the z.ai MCP monthly label

Fixes #115.

Validation

• git diff --check
• Swift tests not run locally (Swift toolchain is not installed on this Raspberry Pi). GitHub CI will validate.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep non-MCP time-window labels

When a z.ai TIME_LIMIT is anything other than the MCP 1-minute marker, this now still reports Monthly; for example the existing maps usage snapshot windows test builds a 30-day TIME_LIMIT and expects 30 days window, so the suite will fail and real non-1-minute time limits lose their accurate label. Gate the override to the specific MCP/monthly case instead of applying it to every .timeLimit.

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