When I attach an image diff with Attach keyword, the report comparator has the height of the shortest image

Hi everybody,

I'm using `allure-robotframework==2.15.2` with `robotframework==7.3.2`
My report is generated with allure-commandline version 2.34.1 `npx --yes allure-commandline generate`

When I attach images (diff, expected, actual) with Attach keyword, then the images displayed in "Show overlay" mode are too short. The bottom of the biggest images is hidden. I have to set the effective size of the `//div[@class="screen-diff__overlay screen-diff__container"]` to show it completely.

For example I've two images with different sizes :

- left img **2109px**
- right img **1907px**
- Comparator size **1926.9px** `//div[@class="screen-diff__overlay screen-diff__container"]`

I expect the comparator height to be at least **2109** instead of **1926**

I don't know if the issue is on allure report or in the listener allure-robotframework

Here is my snipet :
```
${dico}= Create Dictionary expected=data:image/png;base64,${expected_Base64}
... actual=data:image/png;base64,${actual_Base64} diff=data:image/png;base64,${diff_Base64}

${discoAsString} = Convert To String ${dico}
${discoAsStringDoubleQuote} Replace String ${discoAsString} ' "
${dicoAsJson} Convert String To Json ${discoAsStringDoubleQuote}
AllureLibrary.Attach ${discoAsStringDoubleQuote} name=Screenshot diff
... attachment_type=application/vnd.allure.image.diff
```

Thanks for feedback

Reproduce the image-diff attachment with the supplied allure-robotframework, Robot Framework, and allure-commandline versions, using the expected, actual, and diff images of different heights. Determine whether the comparator behavior belongs to the Python listener or the generated report, then verify that Show overlay displays the full height of the tallest image.

Written by the indexing model from the issue text.