Improve Error Handling with Specific Error Messages

[AndreaGriffiths11]

Description

Enhance error handling throughout the extension to provide more specific, actionable error messages for different failure scenarios.

Acceptance Criteria

• Create custom error classes for different failure types
• Improve error messages in gatherRepositoryData() method
• Add retry logic for transient failures
• Show contextual help links in error messages
• Log detailed diagnostics to output channel
• Add error telemetry (opt-in)

Error Categories to Handle

• Network/API failures
• Authentication issues
• Rate limiting
• Invalid repository state
• MCP service unavailable
• AI service errors

Technical Notes

• Extend existing ErrorHandler utility
• Use discriminated unions for error types
• Follow VS Code error message conventions
• Preserve stack traces for debugging

Files to Modify/Create

• src/utils/error-handler.ts - Extend with custom errors
• src/core/copilot-mcp-service.ts - Improve error handling
• src/core/expertise-analyzer.ts - Add specific error cases

Demo Value

Demonstrates Copilot coding agent's ability to:

• Improve code quality
• Implement defensive programming
• Create type-safe error handling
• Follow best practices