[Bug] Anthropic API Error: HTTP 403 Missing Scope for MCP Design Endpoint

**Bug Description**
"Max account OAuth token gets HTTP 403 'missing scope' from api.anthropic.com/v1/design/mcp; works in the app, first-party MCP so Reconnect never re-consents; worked earlier today, broke after re-login." Also, when I do /login (after logging out on the web... I tap Login with Google... and the Google 'select account' modal appears, but the claude page changes the the "Authorize" page... WITHOUT me even finishing the Google Auth process.

**Environment Info**
- Platform: win32
- Terminal: windows-terminal
- Version: 2.1.236
- Feedback ID: 85709889-08e9-48f7-bbb4-6cdaf179168d

**Errors**
```json
[Failed to reconnect to claude-design: api.anthropic.com rejected your claude.ai login (HTTP 403). Your token may be missing a scope this server needs — run /login and retry, or check that your account has access.]
```

No source file or test is identified. Start by reproducing the /login flow and the claude-design reconnect against api.anthropic.com/v1/design/mcp, then trace where the 403 missing-scope error is surfaced. Done means re-login waits for Google authentication to finish and reconnect no longer fails because of the reported scope.

索引モデルが issue の本文から書いたものです。