Document Card image source and position controls in Fern Editor

[devin-ai-integration]

Fern Editor now lets technical writers configure a Card's image without switching to source editing: the Card properties popover exposes a Source field and an Image Position selector (top, left, right, bottom), with repo-relative paths resolving in the editor and the preview matching the published Card component. This PR documents that capability on the Fern Editor page and adds the Docs changelog entry.

Implements docs for: feat(editor): add card source and image position to the visual editor (fern-api/fern-platform#14185)

Summary

• visual-editor.mdx: one sentence after the Supported components table noting the Card properties panel edits image Source and Image Position, linking to the canonical Cards page rather than duplicating its property reference (src/imagePosition/imageWidth/imageHeight are already documented there).
• New changelog entry fern/products/docs/pages/changelog/2026-08-28.mdx (## Card images in Fern Editor, tags developer-tools, components, Button linking to /learn/docs/writing-content/fern-editor#supported-components).

Testing

• pre-commit run --files <changed files>: Vale passed; only pre-existing warnings on untouched lines of visual-editor.mdx.
• (cd fern && npx --yes fern-api@5.59.0 check --warnings): 0 errors; all warnings pre-existing and unrelated to changed files.

Link to Devin session: https://app.devin.ai/sessions/2709a9cf97b94ed598c0ceaefd9eb06c
Open in Devin Desktop: https://app.devin.ai/desktop/session/2709a9cf97b94ed598c0ceaefd9eb06c?variant=devin

[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1787936780-fern-editor-card-image-controls.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/docs/changelog/2026/8/28