Keep job-chaining diagrams available during Mermaid service outages

[rmcdaniel]

Problem

The live Laravel Job Chaining vs. Fan-Out/Fan-In article loads its theme-specific diagrams from mermaid.ink at request time. During visual review after main@3fc6f27e82940af862e95c7d4c2a45f5d3ff9e8a, those image requests intermittently returned HTTP 503. A material fan-out/fan-in diagram rendered only its alt text and the browser emitted resource errors. Later requests succeeded, confirming an intermittent availability dependency rather than a permanently invalid URL.

Acceptance criteria

• Serve the article's diagrams from deployment-owned assets or an equivalently controlled cache so a third-party Mermaid renderer outage cannot remove them from the page.
• Preserve readable light and dark presentation, meaningful alt text, the existing article URL, and its search metadata.
• Add production-browser coverage for the article's rendered diagrams in light and dark themes at desktop and mobile widths; fail when a selected diagram is missing or an image subresource returns an error, without coupling the check to prose wording.

Delete when

Both diagrams render from Durable Workflow-controlled delivery on the live article in light and dark themes at desktop and mobile widths, with no diagram-related HTTP or console errors.