Fix release publish workflow

[mashbean]

Summary

• Publish @matters/matters-editor@0.3.3 with an explicit latest dist-tag so npm accepts the 0.3.x release line even though older 1.x versions exist in the registry.
• Update demo artifact upload/download actions from v3 to v4 to avoid the deprecated action failure on master.

Validation

• git diff --check
• Commit hook ran npm run lint
• Commit hook ran npm test

Context

#523 merged successfully, but the master publish workflow failed at npm publish ./dist because npm requires an explicit tag when publishing 0.3.3 after previously published 1.0.3.