Replace VS Code 'insiders' with 'stable' in test runner

[Copilot]

This PR updates the test runner to use the stable version of VS Code instead of the insiders version for running extension tests.

Changes Made

• Updated test/runTest.ts to use downloadAndUnzipVSCode('stable') instead of downloadAndUnzipVSCode('insiders')

Why This Change?

Using the stable version of VS Code for tests provides:

• More consistent and reliable test execution
• Better compatibility with production environments
• Reduced likelihood of test failures due to unstable insider builds

Testing

• ✅ Code builds successfully without errors
• ✅ Linting passes without issues
• ✅ Only the intended file was modified (no changes to main.js or tsconfig.json)

This is a minimal change that affects only the test infrastructure and does not impact the extension's functionality.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• update.code.visualstudio.com
  • Triggering command: node ./out/test/runTest.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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[nturinski]

Do not change any files. If changes were made to the main.js, revert them.

[nturinski]

@copilot Do not change any files. If changes were made to the main.js, revert them.

[Copilot]

@copilot Do not change any files. If changes were made to the main.js, revert them.

I've verified that main.js was not changed in my commits. The git diff shows that only test/runTest.ts was modified between the base commit and my changes (commit 77aa6a9). main.js remains in its original state.