fix(tools): normalize line endings on document write and replace operations

[Gh61]

Hi, thank you for this extension. I use it almost daily when working with Visual Studio.
I came across an issue that has been causing some inconvenience, so I tried to implement a fix for it.
More details are below.

Description

Agents receive document content with LF line endings but write back with LF regardless of the document native line ending (CRLF on Windows).
This caused two issues:

• document_write and editor_insert silently converted CRLF files (or its parts) to LF
• editor_replace might fail to find multi-line patterns because \n in the search text didn't match \r\n in the document buffer

Changes:

• detect document line ending via VS ITextBuffer snapshot (same source as the status bar CRLF/LF indicator), with content scan as fallback
• normalize incoming content to the document native line ending indocument_write, editor_replace, and editor_insert
• document_read now consistently outputs LF so agents always see \n

Type of Change

• feat - New feature
• fix - Bug fix
• docs - Documentation only
• refactor - Code change that neither fixes a bug nor adds a feature
• test - Adding or updating tests
• chore - Maintenance tasks
• ci - CI/CD changes

Checklist

• My code follows the project's code style
• I have tested my changes locally
• I have updated documentation if needed
• My commits follow the conventional commit format
• This PR has a descriptive title using conventional commit format