Support generic Claude usage windows and scoped limits

[jacobcxdev]

Summary

• Parse Claude usage payloads from dynamic backend-fed window keys instead of a fixed schema
• Add support for limits arrays and scoped model/surface buckets, including future model-specific windows
• Keep existing window normalization for known aliases like omelette → design
• Expand parser tests for new scoped windows, null windows, and limit-based inputs

Testing

• Added parser coverage for future backend-fed model windows
• Added parser coverage for limits array windows and null handling
• Existing usage parser tests still validate known window mappings