fix: safely serialize webview initialization data

[Yan233th]

When config paths contain \u (e.g. \uv) on Windows, a SyntaxError will be thrown because webview script will tries to parse \u as a unicode escape.
So I fixed it by using JSON.stringify instead of injecting raw settings strings into scripts.
Also added tests for Windows path escaping.

Acknowledge

• I have manually written, without the help of an LLM, the pull request description clearly and succinctly.
• I have carefully reviewed the code myself, and ensured the changes are correct and well-tested (including manual testing).
• I have not made any unintentional changes (package.json changes, lockfile changes, .vscode changes, etc.).
• Any new features and settings introduced have been documented in the docs markdown(s) with screenshot(s) where useful, manually, without the use of AI to write the docs.

[agrawal-d]

Thanks