[Bug]: Docs page not full height in Firefox ESR (140.7esr) after 10.2.x update

Describe the bug

There seems to have been a regression somewhere in the Storybook canvas/viewport styles that affects the current Firefox ESR version (140.7esr), where the height of the viewport is no longer full height, rather it is vertically centered 100px high iframe.

Here's how the docs page looks like in the specified Firefox version:

And the Story page view:

Reproduction link

https://main--64b56e737c0aeefed9d5e675.chromatic.com/

Reproduction steps

1. Go to above link in Firefox ESR (140.7esr)
2. See the problem

System

I think this info is mostly unrelevant, the issue happens on Windows 11 in Firefox ESR 140.7esr version.

│  System:
│  OS: Linux 5.15 Ubuntu 22.04.5 LTS 22.04.5 LTS (Jammy Jellyfish) [note: actually Windows 11, this is WSL system info]
│  CPU: (16) x64 12th Gen Intel(R) Core(TM) i7-1270P
│  Shell: 5.8.1 - /usr/bin/zsh
│  Binaries:
│  Node: 24.12.0 - /home/mihkel/.nvm/versions/node/v24.12.0/bin/node
│  npm: 11.7.0 - /home/mihkel/.nvm/versions/node/v24.12.0/bin/npm <----- active
│  pnpm: 9.15.4 - /home/mihkel/.local/share/pnpm/pnpm
│  Browsers:
│  Chrome: 139.0.7258.127
│  npmPackages:
│  @storybook/addon-designs: ^11.1.1 => 11.1.1
│  @storybook/addon-docs: ^10.2.3 => 10.2.3
│  @storybook/addon-links: ^10.2.3 => 10.2.3
│  @storybook/addon-themes: ^10.2.3 => 10.2.3
│  @storybook/react-vite: ^10.2.3 => 10.2.3
│  eslint-plugin-storybook: ^10.2.3 => 10.2.3
│  storybook: ^10.1.10 => 10.2.3

Additional context

In latest Firefox and Chrome, etc, it's working as expected: