BREAKING:
- `formats: FormatQuality[]` -> `format: FormatQuality | null` (singular)
- `replaceOriginal` removed — when `format` is set, the original is always
  replaced via Payload's native `upload.formatOptions`
- `imageOptimizer.variants` field removed (additive multi-format variants were
  local-disk-only; on cloud storage they silently skipped)
- `imageOptimizer.status` enum narrowed from
  ['pending', 'processing', 'complete', 'error'] to ['complete', 'error']
- `afterChange` hook + `convertFormats` task removed

UNCHANGED (the plugin's actual value):
- clientOptimization (Canvas pre-resize before upload)
- generateFilename + uuidFilename / seoFilename / timestampFilename
- generateThumbHash (now always inline)
- regenerateButton UI + stop button
- ImageBox / getOptimizedImageProps / createVariantLoader
- Config-injection defaults for resizeOptions / formatOptions / withMetadata
- adminThumbnail 'auto' + responseHeaders 'immutable' presets
- All REST endpoints

Full migration guide in MIGRATION.md.

96/96 automated tests pass (7 unit + 1 integration + 1 e2e admin smoke).
Build clean. No runtime dependencies changed.