Add comprehensive issue troubleshooting guidelines for MSAL Android

[Copilot]

Consolidates troubleshooting patterns from 181+ closed issues into a structured reference guide for GitHub Copilot, maintainers, and contributors.

Document Structure

.github/copilot-issue-guidelines.md (1,461 lines)

Issue Categories with Symptom → Root Cause → Solution Patterns

• Authentication Flow Failures - Redirect URI encoding mismatches, browser requirements, callback lifecycle issues
• Initialization/Manifest/Config - JSON validation, file placement, client ID format, intent filter configuration
• Token Acquisition & Refresh - Account caching, scope validation, token expiration, claims configuration
• Broker & Company Portal - Installation verification, signature hash matching, SSO setup
• Device/SSO/Registration - Azure AD device registration, Intune enrollment, MAM policies
• Crashes & ANRs - Null safety in callbacks, fragment lifecycle, threading, memory leaks

Support Materials

• Universal Troubleshooting Checklist - 35+ verification points covering configuration, Azure AD, code implementation
• 7 Response Templates - Initial response, configuration errors, token issues, broker problems, crashes, resolution, escalation
• Error Code Reference Table - 10 frequent MSAL errors with immediate fixes
• 77 Code Examples - Correct patterns vs. common mistakes

Example Usage

### Symptom: NO_ACCOUNT_FOUND Error

**Root Cause:** No cached account exists

**Solution:**
```java
// Must use interactive acquireToken first
AcquireTokenParameters params = new AcquireTokenParameters.Builder()
    .startAuthorizationFromActivity(activity)
    .withScopes(Arrays.asList("User.Read"))
    .withCallback(callback)
    .build();
mPCA.acquireToken(params);

Enables consistent, code-specific responses with reduced diagnosis time.

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<details>

<summary>Original prompt</summary>

> Create a new file named .github/copilot-issue-guidelines.md in the repository. The file should include consolidated troubleshooting and response guidance for Copilot and maintainers, spanning frequent errors, root causes, solutions, and answer templates found in 181 closed issues tagged with errors, crashes, and unexpected behavior. Guidelines should include grouped entries for auth flow failures, initialization/manifest/config problems, token issues, broker/company portal problems, device/SSO/registration, crashes/ANRs, and a universal troubleshooting checklist, using markdown structure as previously drafted.


</details>

*This pull request was created as a result of the following prompt from Copilot chat.*
> Create a new file named .github/copilot-issue-guidelines.md in the repository. The file should include consolidated troubleshooting and response guidance for Copilot and maintainers, spanning frequent errors, root causes, solutions, and answer templates found in 181 closed issues tagged with errors, crashes, and unexpected behavior. Guidelines should include grouped entries for auth flow failures, initialization/manifest/config problems, token issues, broker/company portal problems, device/SSO/registration, crashes/ANRs, and a universal troubleshooting checklist, using markdown structure as previously drafted.

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