obs: the plugin targets OBS 31.1.1 while Linux CI links against nixpkgs' 32.1.2

[kixelated]

Split out of a review finding on #2867 (CodeRabbit flagged the stale pin; the divergence below is what makes it worth its own issue).

The two versions

• cpp/obs/buildspec.json pins obs-studio 31.1.1. That's what the obs-deps download gives a macOS or Windows build, so it's the libobs the released plugin binaries link against.
• nixpkgs currently carries obs-studio 32.1.2, which is what a Linux just obs build and the new obs.yml gate link against.
• flake.nix's libobs-headers also pins 31.1.1, matching buildspec.json (feat(obs): compile the plugin in CI, and type-check it without obs-deps #2867 added a guard in just obs check that fails if those two drift).

So the Linux compile gate and the shipped macOS/Windows binaries are a major OBS release apart. Nothing has broken yet, but that gap is exactly where a libobs API change gets through CI and shows up only in a release build, on the platforms with no compile gate at all.

What to do

Bump cpp/obs/buildspec.json to the current stable (32.2.2 at time of writing) and move libobs-headers in flake.nix in the same commit. Needs:

• new hashes for the obs-studio, prebuilt obs-deps and Qt6 archives (macOS + Windows entries), and the nix fetchzip hash;
• a check that libobs/obsconfig.h.in and frontend/api/obs-frontend-api.h are still where libobs-headers expects them;
• a real just obs build on macOS, since that's the platform the release actually ships and the one PR CI never compiles.

just obs check will fail until both pins move together, which is the intended tripwire rather than an obstacle.

(written by Opus 5)

[coderabbitai]

🔗 Related PRs

#1977 - feat(obs): vendor the OBS plugin in-tree under cpp/obs [merged]
#2606 - fix(libmoq): retain CUDA kernel in Nix source [merged]
#2661 - fix(obs): track the matching libmoq version [merged]
#2715 - ci: drop Intel macOS release targets [merged]
#2867 - feat(obs): compile the plugin in CI, and type-check it without obs-deps [open]

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