Refresh Marketplace icon

[Hanjo92]

Summary

• Replace the extension icon with a new flame, Git branch, and review-check design.
• Regenerate the packaged 256x256 PNG from the updated SVG source.
• Bump Marketplace package version to 0.0.13 and update the local VSIX install command.

Marketplace

• Published hanjo92.git-roast-reviewer v0.0.13 successfully.
• --skip-duplicate re-run confirmed version 0.0.13 is already published.
• Marketplace URL: https://marketplace.visualstudio.com/items?itemName=hanjo92.git-roast-reviewer

Test Plan

• Visual check of assets/icon.png
• npm run check
• npm audit --omit=dev
• npm run package
• npx vsce publish --packagePath git-roast-reviewer-0.0.13.vsix
• npx vsce publish --packagePath git-roast-reviewer-0.0.13.vsix --skip-duplicate

Closes #39