Add VS Code for the Web support

[Perdolique]

Summary

Add support for VS Code for the Web, including vscode.dev, github.dev, and browser-hosted Codespaces.

Motivation

The runtime source uses the VS Code API and does not require Node.js APIs, but the extension currently exposes only a desktop main entry point. A web extension requires a single-file browser entry point.

Scope

• Produce a browser-targeted, single-file CommonJS bundle with vscode externalized.
• Add the browser manifest entry while retaining the desktop main entry.
• Reuse the same analysis and configuration source across desktop and web hosts.
• Declare virtual-workspace support only after behavior is verified.
• Add web Extension Host tests for TypeScript and JavaScript documents.
• Include the browser build and its source map policy in packaging and CI.

Acceptance criteria

• The extension installs and activates in a VS Code web extension host.
• Zero-reference findings work with the TypeScript/JavaScript providers available in vscode.dev or github.dev.
• Desktop behavior and package size remain within the existing regression expectations.
• The web bundle contains no Node.js runtime dependency or unnecessary polyfill.
• CI runs at least one browser-hosted Extension Host test suite.

Out of scope

• Adding a custom language server.
• Supporting languages whose web reference provider is unavailable.