Management auth file upload does not propagate priority to runtime auth

[xj999]

Summary

When updating an OAuth auth file through the management upload flow, the top-level priority field is written to the JSON file, but it is not consistently propagated to the runtime auth Attributes["priority"].

As a result, scheduler selection can still treat the uploaded auth as priority 0, even though the file already contains a higher priority value.

Affected flow

Management auth file upload / rewrite flow:

• POST /v0/management/auth-files

Expected behavior

If an uploaded auth file contains:

{
  "type": "codex",
  "email": "user@example.com",
  "priority": 98
}

then the runtime auth used by the scheduler should also have:

• Metadata["priority"] = 98
• Attributes["priority"] = "98"

so scheduler priority selection matches the file content.

Actual behavior

The JSON file is updated correctly, but runtime auth can miss Attributes["priority"], so selection still behaves as if priority is 0.

Reproduction

1. Create or upload an OAuth auth file with top-level "priority": 98
2. Keep another credential available with lower configured priority, for example priority: 9
3. Send requests to a model both credentials support
4. Observe that the lower-priority credential is still selected

Root cause

The management upload/rebuild path does not use the same file-to-auth synthesis logic as the watcher file-loading path, so auth-file-derived runtime fields like priority are not consistently translated into runtime auth attributes.

Fix

PR: #2923