feat: create an IDE plugin for type-test errors

[martyy-code]

Description

Create a VS Code plugin (and consider JetBrains IDE support) that renders type-test failure messages inline, with direct links to the relevant documentation in the web app cookbook.

Why

When tsc fails on a type test, developers see a wall of cryptic compiler output. An IDE plugin can parse the error, render it as a readable diff (expected vs received), and offer a "Learn more" link to the cookbook page for that type pattern.

Acceptance criteria

• VS Code extension published on the Marketplace
• Inline rendering of expected vs received for type mismatches
• "Learn more" links to the cookbook (see docs: transform the web app into a Type Testing Cookbook #52)
• JetBrains support if feasible

Risks

• High effort. IDE plugins require maintenance, marketplace setup, and ongoing compatibility work.

Related

• feat: improve type-test error messages to be actionable #53 (improve error messages)
• docs: transform the web app into a Type Testing Cookbook #52 (web app cookbook)