fix(vscode): use absolute URL for README icon (#464)

* feat(vscode): prepare VS Code extension for marketplace publish

- Remove `private: true` to enable publishing
- Add homepage, galleryBanner, update category to AI, bump version
- Fix .vscodeignore monorepo leak (was packaging 548 files from parent workspace)
- Upgrade @vscode/vsce to ^3.7.1 (fixes .cjs entry point validation)
- Rewrite README for marketplace with CloudFront-hosted screenshots and GIF
- Replace 128x128 placeholder icon with proper 256x256 icon
- Add VS Code tab to marketing site hero section with marketplace link
- Add VS Code SVG icon to marketing assets

For provenance purposes, this commit was AI assisted.

* fix: clean up HeroSection linkEl reference and unused variable

For provenance purposes, this commit was AI assisted.

* fix(vscode): use absolute URL for README icon

Marketplace resolves relative paths against repo root, not the extension
subdirectory, causing a broken image.

For provenance purposes, this commit was AI assisted.

apps/vscode-extension/README.md

@@ -1,5 +1,5 @@
 <p align="center">
-  <img src="images/icon.png" alt="Plannotator for VS Code" width="128" />
+  <img src="https://d17ygohy796f9l.cloudfront.net/vscode/icon.png" alt="Plannotator for VS Code" width="128" />
 </p>
 
 <h1 align="center">Plannotator</h1>