Permanently allowed URLs (and other permissions) are not persisted across sessions

### Describe the bug

URL permissions marked as "permanent" (e.g., https://docs.github.com) do not persist across sessions.

### Affected version

GitHub Copilot CLI 1.0.45.

### Steps to reproduce the behavior

Steps to reproduce:

1. In a session, when prompted for URL access, choose "Allow permanently"
2. Start a new session in the same directory
3. The same URL permission is requested again

Root cause observed:
- The permanent choice writes to settings.json → allowedUrls, but permissions-config.json (which appears to be checked at runtime) has no corresponding web_fetch/URL entry. This split causes the permission to be ignored on next session start.

Files involved:
~/.copilot/settings.json (has allowedUrls) vs ~/.copilot/permissions-config.json (has tool_approvals — no URL entry)

### Expected behavior

When a user selects "Allow permanently" for a URL or tool permission, that permission should be respected in all future sessions without prompting again.

### Additional context

_No response_

Start by tracing how settings.json's allowedUrls and permissions-config.json's tool_approvals are written and loaded between sessions. Reproduce the permanent URL approval, then verify that the corresponding web_fetch/URL permission is persisted and no longer requested in a new session.

由索引模型根据 Issue 内容生成。