ci: restore the full OBS install, and stop passing a Windows SDK to -A

Two more findings from the three-platform run, both from reading the actual
CI logs rather than guessing.

macOS. libobs now builds, installs, and is FOUND by find_package -- and then
every consumer fails with:

  IMPORTED_LOCATION or IMPORTED_IMPLIB not set for imported target
  "OBS::libobs" configuration "Release".

Restricting --install to the libobs subdirectory (the previous commit's fix
for the obs-frontend-api install error) also loses the per-configuration
export file, so libobsTargets.cmake lands without its
libobsTargets-release.cmake sibling and the imported target has no location
for any configuration. The install therefore goes back to the whole build
tree, exactly as upstream does, with its exit code tolerated: it gets all the
way through libobs and only then trips over the install rule of a target this
build deliberately skips. If libobs genuinely did not install,
find_package(libobs) in the top-level CMakeLists is where that surfaces, with
a far better message than a half-installed tree.

Belt and braces, the top-level CMakeLists also picks up
obs-plugintemplate's CMAKE_MAP_IMPORTED_CONFIG_* fallbacks, so an imported
target exported under a different configuration name still resolves.

Windows. The sub-configure was re-entering obs-studio's OWN dependency
downloader with a corrupted architecture:

  string sub-command JSON member 'hashes windows-x64,version=10.0.26100.0'
    not found
  Unable to download .../windows-deps-2023-11-03-x64,version=10.0.26100.0.zip

Upstream passes "-A x64,version=<Windows SDK>", and with a current CMake that
",version=" suffix comes back out verbatim in the sub-build's
CMAKE_VS_PLATFORM_NAME -- which obs-studio keys its release assets off. Plain
"-A x64" now. The Windows SDK is selected automatically anyway ("Selecting
Windows SDK version 10.0.26100.0" in the same log), and CMAKE_SYSTEM_VERSION
is passed explicitly.

The macOS job also lists the installed libobs export directory, so the next
run answers "which target files actually landed" from CI output instead of
inference.

Linux remains green and unaffected: ctest 6/6.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RL8abRmgFXkVASHkkqiJbE

.gitea/workflows/build.yml

@@ -79,6 +79,7 @@ jobs:
 
       - name: Show what was built
         run: |
+          ls -la .deps/Frameworks/libobs.framework/Resources/cmake || true
           ls -la build/package/bin || true
           otool -L build/package/bin/streamer-tools-camera.so || true