fix(ui): improve system info client RAM/OS/browser fallback

[FixleCH]

Summary

• Improve client info in UIWindowSystemInfo.js
• Avoid RAM: Unknown when navigator.deviceMemory is missing
• Avoid OS: Linux Unknown when platformVersion is not provided
• Avoid Browser: Not-A.Brand, prefer meaningful UA hint or navigator.userAgent fallback

Changes

• getClientInfo():
  • ram:
    • use navigator.deviceMemory if available
    • fall back to window.performance.memory.jsHeapSizeLimit if available
    • otherwise 'Unknown'
  • browser brand:
    • pick first non-Not-A.Brand entry from uaData.brands
    • infer browser from navigator.userAgent if result is generic/noisy
  • os text:
    • generate OS as platform only when platformVersion is absent

Why

Avoid flaky client system info displayed in the widget for modern privacy-oriented browsers and old browser fallbacks.

Testing

• manual flows:
  • UA Client Hints both valid and Not-A.Brand
  • navigator.deviceMemory both present and absent
  • compare UI output in widget
• verified no console errors on refresh cycles

Notes

• this is best-effort; client-side memory reporting is inherently approximated by browser APIs.

[CLAassistant]

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