2026 09 06 Editor Content And Service Defaults

<!-- entry: {"id":"2026-09-06-equation-values","kind":"fix","migrationNotes":[]} -->

• equation-node, equation-node-static: Preserve string, number and boolean equation content in editable, static and document views; display missing or unsupported values as empty.

<!-- entry: {"id":"2026-09-06-image-downloads","kind":"fix","migrationNotes":[]} -->

• media-preview-dialog: Download supported image destinations while preserving relative, HTTP, HTTPS, blob, and image data URLs.

<!-- entry: {"id":"2026-09-06-ai-credentials","kind":"behavior","migrationNotes":[]} -->

• ai-api, copilot-api: Use the caller's AI Gateway key supplied through editor settings or the request body.

<!-- entry: {"id":"2026-09-06-upload-authorization","kind":"behavior","migrationNotes":[]} -->

• media-uploadthing-api: Allow uploads during local development; require application authorization before enabling production uploads.

<!-- entry: {"id":"2026-09-06-drag-targets","kind":"fix","migrationNotes":[]} -->

• column-node, table-node: Ignore drop checks without a source editor node.