Updated `copilot-instructions.md` to include new guidelines for Markdown documentation and testing practices. Modified the `DocumentChunk` record in `DocumentChunk.cs` to add `PageNumber` and `IndexOnPage` properties. Adjusted `GetChunksAsync` and `GetChunkEmbeddingAsync` methods in `DocumentService.cs` to accommodate the new properties.
Enhance `copilot-instructions.md` to include updated best practices for code suggestions, style, architecture, documentation, and testing. Key changes emphasize high confidence suggestions, the latest C# features, specific formatting preferences, and comprehensive documentation requirements. Additionally, new testing practices are introduced to streamline unit test additions and ensure code quality.