Improve handling of 404 errors from Apple developer website

[mattt]

No description provided.

[Copilot]

Pull Request Overview

This PR improves error handling for 404 responses from the Apple developer website by introducing a custom NotFoundError exception and providing user-friendly error responses with helpful guidance.

• Adds a custom NotFoundError class to distinguish 404 errors from other HTTP errors
• Implements specific 404 handling that throws NotFoundError when Apple documentation pages are not found
• Provides enhanced error responses with helpful guidance and example URLs for both JSON and markdown content types

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/lib/fetch.ts	Adds NotFoundError class and throws it specifically for 404 responses from Apple documentation
src/index.ts	Imports NotFoundError and adds comprehensive error handling with user-friendly 404 responses

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[Copilot]

The hardcoded domain 'sosumi.ai' in the example URLs should be dynamically determined from the request context to ensure accuracy across different deployment environments.