docs: add known issue and hotfix for opencode-openai-codex-auth 400 error

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

README.ko.md

@@ -166,6 +166,18 @@ opencode auth login
 # 브라우저에서 OAuth 플로우 완료
 ```
 
+**⚠️ 알려진 이슈**: 현재 공식 npm 패키지에 400 에러(`"No tool call found for function call output with call_id"`)를 유발하는 버그가 있습니다. 수정 버전이 배포될 때까지 **핫픽스 브랜치 사용을 권장합니다**. `~/.config/opencode/package.json`을 수정하세요:
+
+```json
+{
+  "dependencies": {
+    "opencode-openai-codex-auth": "code-yeongyu/opencode-openai-codex-auth#fix/orphaned-function-call-output-with-tools"
+  }
+}
+```
+
+그 후 `cd ~/.config/opencode && bun i`를 실행하세요. `opencode.json`에서는 버전 없이 `"opencode-openai-codex-auth"`로 사용합니다 (`@4.1.0` 제외).
+
 #### 4.4 대안: 프록시 기반 인증
 
 프록시 기반 인증을 선호하는 사용자를 위해 [VibeProxy](https://github.com/automazeio/vibeproxy) (macOS) 또는 [CLIProxyAPI](https://github.com/router-for-me/CLIProxyAPI)를 대안으로 사용할 수 있습니다.

README.md

@@ -165,6 +165,18 @@ opencode auth login
 # Complete OAuth flow in browser
 ```
 
+**⚠️ Known Issue**: The official npm package currently has a bug that causes 400 errors (`"No tool call found for function call output with call_id"`). Until a fix is released, **use the hotfix branch instead**. Modify `~/.config/opencode/package.json`:
+
+```json
+{
+  "dependencies": {
+    "opencode-openai-codex-auth": "code-yeongyu/opencode-openai-codex-auth#fix/orphaned-function-call-output-with-tools"
+  }
+}
+```
+
+Then run `cd ~/.config/opencode && bun i`. In your `opencode.json`, use the plugin name without a version: `"opencode-openai-codex-auth"` (not `@4.1.0`).
+
 #### 4.4 Alternative: Proxy-based Authentication
 
 For users who prefer proxy-based authentication, [VibeProxy](https://github.com/automazeio/vibeproxy) (macOS) or [CLIProxyAPI](https://github.com/router-for-me/CLIProxyAPI) remain available as alternatives.