[Core:#3] Error handling for publish failures

[wiatrM]

🔗 Linked Issue

This implements error handling requirements from contextmesh-core#3

User Story

I get clear error messages if publishing fails.

Priority

Must Have (M)

Estimated Effort

1 developer day

Acceptance Criteria

• Reports JSON Schema errors with actionable hints
• Handles network issues gracefully
• Provides clear error messages for common failures
• Includes line numbers for validation errors
• Suggests fixes for common problems

Technical Requirements

• Custom error classes for different failure types
• Structured error responses
• User-friendly error formatting
• Logging for debugging

Implementation Details

Error Classes Structure

src/errors/
├── base.ts         # Base error class
├── validation.ts   # JSON Schema validation errors
├── network.ts      # API communication errors
├── auth.ts         # Authentication errors
├── filesystem.ts   # File system errors
└── index.ts        # Export all error types

Error Response Format

{
  code: 'VALIDATION_ERROR',
  message: 'User-friendly error message',
  details: {
    field: 'connector.name',
    line: 15,
    column: 8,
    suggestion: 'Name must be lowercase with hyphens'
  },
  stack?: 'Full stack trace when --verbose'
}

Definition of Done

• Custom error handling for all failure scenarios
• JSON Schema validation errors show line numbers
• Network errors provide retry suggestions
• Authentication errors guide to re-auth
• File system errors are user-friendly
• Unit tests for error scenarios
• Error messages tested with real users
• Documentation covers common errors

Related Core Issue

https://github.com/cloudfloo/contextmesh-core/issues/3