test(vscode): pre-release validation and smoke tests

[jscaltreto]

Parent: #33

Summary

Validate the extension works end-to-end from a packaged VSIX before first publish.

Work

• Run end-to-end install test from packaged .vsix on a clean VS Code setup
• Review command names, setting names, and user-facing copy for anything too dev-oriented
• Verify extension packaging doesn't rely on local-only artifacts
• Decide whether we need smoke tests or extension integration tests beyond compile/package
• Confirm the current feature set is sufficient for a first public release (or flag gaps)