issue 4531 slice 34: PublishingShell demand-publish content ids #4858

Parent: #4531

Slice goal

On Publishing Runtime, the operator picks an edition, enters one or more content ids, and demand-publishes them. Success and HTTP errors are visible. Chrome uses the publishing message catalog (not raw English).

Out of scope

Start/stop edition, incremental queue, full-edition start, log export.

Acceptance

• Demand publish submits the chosen edition plus the parsed content ids.
• Empty id list does not call the server.
• Errors stay on the Runtime section.
• H2 surface-filtered Playwright spec.
• product-docs note under product-docs/8.2.
• Update parent [8.2] Unified publishing — next React increments #4531 Agent progress.

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