[codex] fix workbench mobile image previews

[joeymilano]

What changed

• Tightened the Workbench layout for mobile widths so cards, inputs, selectors, and action controls no longer force horizontal scrolling.
• Preserved the newly merged Agnes AI image generation integration while making generated images render across all social mockup previews.
• Fixed image preview propagation for X, Reddit, Newsletter/Substack, and Threads, and kept image containers responsive on small screens.

Why

The Workbench could overflow on mobile because nested grid/flex children and long labels were allowed to keep oversized minimum widths. The image generation PR also introduced platform previews where some generated image URLs were accepted but not actually rendered.

Validation

• npm run typecheck
• npm test
• npm run build

Notes

Image generation secrets are intentionally not committed. Production needs IMAGE_API_KEY configured as a deployment secret. IMAGE_API_BASE and IMAGE_MODEL are already present in config.

[cloudflare-workers-and-pages]

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