The .gitignore commit was never pushed to the FSR2 fork, breaking CI
shallow clones. Revert to 3d22aef and add ignore=dirty to .gitmodules
to suppress generated shader header noise.
Both repos were previously untracked clones under extern/ that users had
to fetch manually. Adding them as submodules ensures git pull --recurse
fetches the correct commits with our format-matching patches.
- FidelityFX-FSR2: standalone FSR2 v2.2.1 upscaler (Kelsidavis fork)
- FidelityFX-SDK: full SDK with FSR3 frame generation (Kelsidavis fork)
- Add vk-bootstrap as a git submodule (was in extern/ but not tracked,
causing "vk-bootstrap not found" on all CI jobs)
- Whitelist extern/vk-bootstrap in .gitignore
- Move stormlib to a separate optional install step on both Windows CI
jobs (mingw-w64-x86_64-stormlib doesn't exist in MSYS2 repos)
