fix: launch VS Code tunnel safely and modernize Node runtime

[sourishkrout]

Summary

• launch the Windows VS Code tunnel through code-tunnel.exe instead of the code.cmd shim
• make macOS VS Code CLI resolution tolerate flattened @vscode/test-electron app bundles
• normalize Unix executable permissions before spawning the VS Code CLI
• remove temporary tunnel probe/debug output and inherit stdio for tunnel commands
• sanitize custom machine names before passing them to VS Code
• move the action/runtime tooling to Node 24
• update CI actions and Node version, plus TypeScript/tsconfig/node typings for the Node 24 baseline
• update tests and rebuild the bundled dist/index.js

Why

GitHub-hosted runners execute JavaScript actions on modern Node runtimes. The previous Windows path failed first on raw .cmd spawning, then the VS Code code.cmd shim failed on hosted Windows with The system cannot find the path specified.

Using code-tunnel.exe directly avoids the shim entirely on Windows. While here, the action metadata and CI are moved off stale Node 16/20 assumptions so the repo tests the runtime GitHub is moving Actions toward.

A local Darwin smoke also exposed that the VS Code test download can return a .app/.../Electron path while the extracted files are flattened under Contents/..., with CLI files lacking executable bits. The action now handles that before spawning.

Verification

• yarn test on Node 24
• yarn run build on Node 24
• INPUT_TIMEOUT=5000 INPUT_MACHINENAME=local-darwin GITHUB_RUN_ID=local-darwin node dist/index.js on Darwin/Node 24
• pre-commit hook: yarn test:lint
• pre-commit hook: yarn run build