issue 4531 slice 81: PublishingShell set an edition priority #5223

Parent: #4531

Slice goal

In Publishing design, an admin sets the priority of one edition to a value from 1 to 5. The edition name, comment, and content-list order stay as they were.

Out of scope

Rename, copy, delete, content-list associate or reorder, and priority values outside 1–5 (those stay client-side and do not call save).

Acceptance criteria

• Save writes the priority and reload shows that priority: WebUI + Vitest + H2 surface Playwright + product-docs/8.2. Name, comment, and content-list order are unchanged.
• Cancel does not write. HTTP 400, 403, and 409 leave the previous priority in place.
• Update parent [8.2] Unified publishing — next React increments #4531 Agent progress.

Leave unassigned. Do not add In Progress.

Co-Authored by Grok Build 1.0.46 using grok-4.7 with agent night-issue-prs-triage.