Sync .gitignore and extensions.json across repos

[sdwheeler]

PR Summary

Sync .gitignore and extensions.json across repos

• Fixes AB#544749

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributors guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

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[learn-build-service-prod]

Learn Build status updates of commit 1489b60:

✅ Validation status: passed

File	Status	Preview URL	Details
.gitignore	✅Succeeded
.vscode/extensions.json	✅Succeeded

For more details, please refer to the build report.

[Copilot]

Pull request overview

This PR synchronizes configuration files (.gitignore and extensions.json) across repositories to maintain consistency in development environments and ignored files. The changes standardize VS Code extension recommendations and gitignore patterns.

Changes:

• Updated VS Code extension recommendations by adding 4 new extensions (Vale, Gremlins, Markdown YAML Preamble, ErrorLens) and removing Markdown PDF
• Reorganized and expanded .gitignore patterns with additional build artifacts, tool directories, and configuration files

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
.vscode/extensions.json	Added development and documentation quality extensions, removed markdown-pdf, reordered list
.gitignore	Expanded ignore patterns for build artifacts and tools, reorganized alphabetically

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