PRU Quota Wiped Out, very likely related to enabling Assisted Permissions

Describe the bug

I believe the issue is very likely related to enabling assisted permissions, since there were no problems before it was turned on.

• Subscription: Copilot Pro (Annual Plan / Legacy Request-based PRU).
• August 11 Incident: With 234 PRUs remaining in my allowance, I sent 1 single prompt, and my remaining quota was instantly wiped out to 0.
• September 2 Incident (Today): My quota reset today for the new billing cycle. I sent 1 single prompt in a brand-new session, and my entire September PRU allowance was instantly wiped out to 0 again.
• Historical Context: Prior to August 11, I had used this annual plan for over 16 months without any issue. This is a newly introduced recurring bug, not a normal usage behavior.

The request consumption shown in Copilot CLI is correct, but the actual backend consumption is wrong.

Affected version

No response

Steps to reproduce the behavior

1. Legacy Request-based PRU Account
2. Switch to Assisted Permissions
3. Send Prompt

Since a single prompt wiped out my entire monthly quota, I’m unable to repeat the test.

Expected behavior

No response

Additional context

Github Support Ticket #4720186

先从 issue 中描述的 assisted-permissions 路径和 quota-consumption 报告开始，然后比较一次 prompt 后 CLI 显示的 request 消耗量与 backend allowance。没有确定具体的源文件或测试，由于 quota 已耗尽，目前无法复现，并且预期行为也未明确说明；因此需要 maintainer 澄清完成标准。