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, 50 insertions, 0 deletions

diff --git a/libs/preview_nif/src/Camera.cpp b/libs/preview_nif/src/Camera.cpp
new file mode 100644
index 0000000..0a9ce73
--- /dev/null
+++ b/libs/preview_nif/src/Camera.cpp
@@ -0,0 +1,50 @@
+#include "Camera.h"
+
+#include <cmath>
+
+void Camera::setDistance(float distance)
+{
+    m_Distance = qBound(MinDistance, distance, MaxDistance);
+    cameraMoved();
+}
+
+void Camera::setLookAt(QVector3D lookAt)
+{
+    m_LookAt = lookAt;
+    cameraMoved();
+}
+
+void Camera::pan(QVector3D distance)
+{
+    m_LookAt += distance;
+    cameraMoved();
+}
+
+void Camera::rotate(float yaw, float pitch)
+{
+    m_Yaw = repeat(m_Yaw + yaw, 0.0f, 360.0f);
+    m_Pitch = repeat(m_Pitch + pitch, 0.0f, 360.0f);
+
+    cameraMoved();
+}
+
+void Camera::zoomDistance(float distance)
+{
+    m_Distance += distance;
+    m_Distance = qBound(MinDistance, m_Distance, MaxDistance);
+
+    cameraMoved();
+}
+
+void Camera::zoomFactor(float factor)
+{
+    m_Distance *= factor;
+    m_Distance = qBound(MinDistance, m_Distance, MaxDistance);
+
+    cameraMoved();
+}
+
+float Camera::repeat(float value, float min, float max)
+{
+    return fmod(fmod(value, max - min) + (max - min), max - min) + min;
+}