Add NIF previewer plugin with Linux-specific fixes

Vendored from github.com/Parapets/mo2-preview_nif and adapted for Linux:

- BSA texture resolution via MO2 virtual tree with case-insensitive
  fallback walk (Linux FS is case-sensitive; NIFs reference textures
  with arbitrary case against files on disk)
- Process-wide cached BSA candidate list, keyed by profile path,
  priority-sorted, filtering disabled mods
- Path backslash normalization before loose-file lookup
- Polygon offset on SLSF1_Decal-flagged shapes to break z-ties with
  coincident base meshes (road decals, moss overlays)
- Opaque framebuffer via glColorMask alpha lock so alpha-blended shapes
  can't bleed the dialog background through the preview area
- QMouseEvent::globalPosition().toPoint() for Qt6 compatibility

Preview dialog behavior (organizercore.cpp):
- Switch previewFile and previewFileWithAlternatives from stack-allocated
  exec() to heap + ApplicationModal + show() + WA_DeleteOnClose.
- Parent passed as nullptr so preview lifetime is decoupled from the
  stack-allocated ModInfoDialog that spawns it. Nested exec() inside
  the enclosing dialog's exec() was softlocking on close.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/libs/preview_nif/.github/workflows/build.yml b/libs/preview_nif/.github/workflows/build.yml
new file mode 100644
index 0000000..4bb1166
--- /dev/null
+++ b/libs/preview_nif/.github/workflows/build.yml
@@ -0,0 +1,28 @@
+name: Build NIF Preview Plugin
+
+on:
+  push:
+    branches: main
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  build:
+    runs-on: windows-2022
+    steps:
+      - name: Build NIF Preview Plugin
+        uses: ModOrganizer2/build-with-mob-action@master
+        with:
+          mo2-third-parties: fmt libbsarch
+          mo2-dependencies: cmake_common uibase
+      - name: Upload Build
+        uses: actions/upload-artifact@v3
+        with:
+          name: preview_nif
+          path: |
+            ./build/modorganizer_super/${{ github.event.repository.name }}/vsbuild/src/RelWithDebInfo/preview_nif.dll
+      - uses: actions/upload-artifact@v3
+        with:
+          name: preview_nif
+          path: |
+            ./build/modorganizer_super/${{ github.event.repository.name }}/**/data/shaders/*