Publish requirements
You cannot publish an empty post. Add at least one content block with real content, then use Publish in the header.
First publish vs updates
On a brand-new post, Publish creates the post in the database and sets it to PUBLISHED, then sends you to the editor URL for that post's id so you can keep iterating.
On an existing post, Publish saves your latest title and blocks, then runs the publish step so subscribers and surfaces that consume the post see the update.
Draft and scheduled statuses
Your Posts list can include DRAFT, PUBLISHED, and SCHEDULED rows. Drafts are work-in-progress; published posts are live; scheduled posts go out when their scheduled time is reached (exact scheduling UI may evolve).
The editor header shows a draft-style status line while you work; use Publish when you want the post to be live.
Leaving the editor
Cancel Edits navigates back to your Posts list without a separate "save draft" button in the header—make sure you've published if you need your latest changes stored on the server before you leave.
If we add explicit "Save draft" or autosave indicators in the header, they will appear alongside Publish; until then, treat Publish as the action that commits your work to your live post pipeline.