feat: auto-persist rotated refresh tokens

[0x7551]

Summary

• Automatically persist rotated OAuth refresh tokens back to config.yaml
• Ensures gateway survives restarts without manual token updates
• Handles both initial token exchange and scheduled auto-refresh rotation

Changes

• src/oauth.ts: add persistRefreshToken() helper, detect token rotation in initOAuth and scheduleRefresh, write new token back to config file

Test plan

• Start gateway — verify initial token refresh works as before
• Simulate token rotation (provider returns new refresh_token) — verify config.yaml is updated
• Verify config file write failure is logged as warning, not fatal

🤖 Generated with Claude Code

[SakuraPuare]

真得要 每次失败了token就无了

[whiletrue0x]

nice，我白天看下。今天发了0.2更新

应该覆盖这个问题了，我double check下