[Bug] Usage limit calculation incorrect for context window consumption

Bug Description
The usage limit system seems broken right now. I pay for the 5x Max plan, but a single chat using just 24% of the 1M context managed to eat up 70% of my 5-hour session right after reset.

Environment Info

• Platform: darwin
• Terminal: WarpTerminal
• Version: 2.1.187
• Feedback ID: bff97b30-7681-47a0-8cd2-bec544875a79

Errors

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<img width="673" height="245" alt="Image" src="https://github.com/user-attachments/assets/f3ddc7a0-12c9-43cc-a803-23c09b6dd630" />

<img width="1200" height="616" alt="Image" src="https://github.com/user-attachments/assets/ba2b3ccc-719a-46b8-a903-f1626cff4820" />