Add reference to official Microsoft identity error codes documentation

Co-authored-by: fadidurah <[email protected]>

Author: Copilot

.github/copilot-instructions.md

@@ -188,6 +188,7 @@ When interacting with users across **any channel** (GitHub issues, web chat, age
 - **Common Issues Guide:** [`issue-responses/common-issues-guide.md`](issue-responses/common-issues-guide.md) - Comprehensive troubleshooting reference
 - **Communication Guidelines:** [`issue-responses/customer-communication-guidelines.md`](issue-responses/customer-communication-guidelines.md) - Response templates for all channels
 - **Automated Workflow:** [`workflows/copilot-issue-response.yml`](workflows/copilot-issue-response.yml) - Automatic issue triage and response
+- **Microsoft Identity Error Codes:** [Official Error Reference](https://learn.microsoft.com/en-us/entra/identity-platform/reference-error-codes) - Use as authoritative source for AADSTS error meanings
 
 ### Quick Issue Diagnosis
 

.github/issue-responses/common-issues-guide.md

@@ -118,6 +118,8 @@ Add the BrowserTabActivity to your AndroidManifest.xml:
 
 **Common AADSTS Errors and Solutions:**
 
+> **📖 Official Reference:** For complete error code definitions and guidance, see [Microsoft Identity Platform Error Codes](https://learn.microsoft.com/en-us/entra/identity-platform/reference-error-codes).
+
 | Error Code | Description | Solution |
 |------------|-------------|----------|
 | AADSTS50011 | Redirect URI mismatch | Verify redirect URI matches Azure App Registration exactly (including encoding) |