Represent Wix wow-image media as core/image instead of custom/responsive-media raw markup

## Symptom

On an imported Wix site (https://www.360chiro.co.uk/, 15 of 16 routes affected), captured `wow-image` media converts to the generated carrier block `custom/responsive-media` with the raw captured anchor markup as its `content` attribute:

```

```

Frontend rendering is fine, but in the editor the block presents as **"CAPTURED MEDIA OR LAYOUT HTML"** with a wall of escaped markup — the image is not editable as an image (no replace/crop/alt editing via native UI).

## Why file it

The completion bar for imports is full editability with native Gutenberg blocks, custom blocks only where a confirmed Gutenberg incompatibility exists. A `wow-image` wrapping a plain `` (with `data-image-info` JSON declaring displayMode/size/URI) has a faithful native representation as `core/image` in the common cases; the responsive-media carrier seems like it should be the last resort, not the default for Wix media.

Related (not duplicates): #867 (editor iframe presentation assets), #1070 (media-forward heroes fall back to fixed-width HTML islands — different trigger).

No file or test is named in the report; search the import/conversion path for `wow-image` and `custom/responsive-media` first. Compare its handling of `data-image-info` and plain `` cases, then add coverage showing eligible Wix media becomes editable `core/image` while unsupported cases retain the carrier.

Written by the indexing model from the issue text.