Use splat hashes for editor overwrite and publish flows

[abstrakt8]

Summary

• Remove editor reliance on internal splat ids for overwrite, settings, and republish flows
• Use hash consistently when loading existing scene settings and republishing
• Stop passing overwriteId through the publish settings dialog

Testing

• npm run lint passed
• npm run build passed

[Copilot]

Pull request overview

This PR updates the publish/overwrite flow to use splat hashes instead of internal splat IDs, aligning editor overwrite, settings, and republish behavior around the hash identifier.

Changes:

• Removed Scene.id and PublishSettings.overwriteId.
• Updated settings fetch/update and republish calls to use overwriteHash.
• Stopped passing overwriteId from the publish settings dialog.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/publish.ts	Switches publish, republish, and settings flows from internal IDs to hashes.
src/ui/publish-settings-dialog.ts	Resolves publish settings with overwriteHash only.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.