Add 'scaled' to the image_size enum in wp-api-generated.js to match the
PHP route registration change, fixing the git diff --exit-code CI check.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add tests for the new 'scaled' image_size enum value in the sideload
endpoint: verifying metadata updates, authentication requirements,
route schema, and unique filename handling for the -scaled suffix.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

get_attached_file() can return false when no file is
attached. Add a guard to return a WP_Error before calling
wp_basename() with a falsy value.

The sideload route uses edit_media_item_permissions_check
which returns rest_cannot_edit_image, not rest_forbidden.

Addresses review feedback to assert the value of
metadata['file'], not just its existence.

Avoids repeating the string literal for the array key
in the enum assertion test.

The $number parameter in filter_wp_unique_filename is
typed as int|string. Casting to (int) before interpolation
into the preg_match pattern ensures regex safety regardless
of any future changes to what $number might contain.

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Check whether _wp_attached_file already matches $path before
calling update_attached_file(), since a false return could
mean the value is unchanged. Return a WP_Error when the meta
value differs but the update still fails.

Per review feedback, use ! is_int( $number ) as the guard
since $number is either an int or an empty string. This is
more precise than empty() and allows removing the (int) cast
in the regex since $number is guaranteed to be an int.

Checks image dimensions and filesize before calling
update_attached_file() to avoid leaving the attachment
in a bad state if the scaled file is unreadable or empty.

Move the literal dash outside the capture group so the regex
reads `/(.*)-(\d+x\d+|scaled)-/` instead of alternating
`(-\d+x\d+|-scaled)`. This keeps the dash handling consistent
and simplifies the filename reconstruction.

Props westonruter.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>