ifcviewer: move camera + surface-geom state into ViewportCore (#84-g)

Move the camera/projection/clear-color fields that buildViewProj,
updateFrameUniforms, the cull screen-area projector, and the bonsai-
side cameraState/setCamera/viewAll surface depend on. Same alias
pattern; no method bodies move in this commit — the next one moves
the camera math methods now that all their state is in core.

State moved (12 fields):
  int   configured_w_, configured_h_
  float camera_target_[3], camera_distance_
  float camera_yaw_deg_, camera_pitch_deg_, camera_fov_y_deg_
  float camera_near_, camera_far_
  bool  projection_ortho_
  Eigen::Vector4f background_color_

ViewportWindow keeps reference aliases for each (including a proper
`float (&camera_target_)[3]` reference-to-array binding) so the
~150 call sites that touch camera state stay unchanged. Aliases
collapse when their owning methods migrate.

Builds: desktop / bonsai / web all green. Tests 100/100.

src/ifcviewer/ViewportCore.h

@@ -197,6 +197,36 @@ private:
     // queued setter that runs before init becomes a no-op rather than
     // crashing on a null device.
     bool wgpu_initialized_ = false;
+
+    // ---- Surface geometry ----------------------------------------------------
+    //
+    // configured_w_/h_ track the device-pixel framebuffer size as last
+    // requested through host_->framebufferSize(). depth + MSAA attachments
+    // are sized against these.
+    int configured_w_ = 0;
+    int configured_h_ = 0;
+
+    // ---- Orbit / fly camera state -------------------------------------------
+    //
+    // Mirrors the GL viewport's defaults; the orbit math lives in
+    // buildViewProj (also in ViewportCore). BIM scenes are +Z up.
+    float camera_target_[3]  = { 0.0f, 0.0f, 0.0f };
+    float camera_distance_   = 50.0f;
+    float camera_yaw_deg_    = 45.0f;
+    float camera_pitch_deg_  = 30.0f;
+    float camera_fov_y_deg_  = 45.0f;
+    float camera_near_       = 0.1f;
+    float camera_far_        = 10000.0f;
+    // Perspective by default; toggleProjection (P key) flips this. When
+    // true, buildViewProj uses an orthographic matrix sized by
+    // camera_distance_ × tan(fov/2) so toggling looks like a smooth
+    // swap rather than a jump in apparent size.
+    bool  projection_ortho_  = false;
+
+    // RGBA in linear-space [0..1]. The render-pass clear value applies
+    // an sRGB-to-linear conversion on top so the on-screen colour
+    // matches the hex value passed via setBackgroundColor.
+    Eigen::Vector4f background_color_ = {0.125f, 0.137f, 0.161f, 1.0f};
 };
 
 #endif  // VIEWPORTCORE_H

src/ifcviewer/ViewportWindow.cpp

@@ -608,7 +608,18 @@ ViewportWindow::ViewportWindow(QWindow* parent)
       next_model_id_  (core_.next_model_id_),
       next_object_id_ (core_.next_object_id_),
       federated_false_origin_meters_(core_.federated_false_origin_meters_),
-      wgpu_initialized_(core_.wgpu_initialized_) {
+      wgpu_initialized_(core_.wgpu_initialized_),
+      configured_w_   (core_.configured_w_),
+      configured_h_   (core_.configured_h_),
+      camera_target_  (core_.camera_target_),
+      camera_distance_(core_.camera_distance_),
+      projection_ortho_(core_.projection_ortho_),
+      camera_yaw_deg_ (core_.camera_yaw_deg_),
+      camera_pitch_deg_(core_.camera_pitch_deg_),
+      camera_fov_y_deg_(core_.camera_fov_y_deg_),
+      camera_near_    (core_.camera_near_),
+      camera_far_     (core_.camera_far_),
+      background_color_(core_.background_color_) {
     // wgpu doesn't need a GL context; we just need a real native window
     // whose backing layer matches the GPU API wgpu will drive.
     //

src/ifcviewer/ViewportWindow.h

@@ -635,8 +635,8 @@ private:
     void recomposeAndUploadModel(uint32_t model_id);
 
     bool& wgpu_initialized_;
-    int  configured_w_ = 0;
-    int  configured_h_ = 0;
+    int& configured_w_;
+    int& configured_h_;
 
     // ---- wgpu lifecycle state aliases ----------------------------------
     //
@@ -869,19 +869,12 @@ private:
     // thread per model.
     mutable std::atomic<int> hiz_trace_budget_{0};
 
-    // 0x20 / 0xff ≈ 0.125, 0x23 / 0xff ≈ 0.137, 0x29 / 0xff ≈ 0.161.
-    Eigen::Vector4f background_color_ = {0.125f, 0.137f, 0.161f, 1.0f};
+    Eigen::Vector4f& background_color_;
 
-    // Camera (orbit, right-handed Y-up world → wait, BIM is +Z up).
-    // Mirrors the GL viewport's defaults; mouse navigation lands later.
-    float camera_target_[3] = { 0.0f, 0.0f, 0.0f };
-    float camera_distance_  = 50.0f;
-
-    // Perspective by default; toggleProjection() (P key) flips this. When
-    // true, the per-frame projection builder uses an orthographic matrix
-    // sized by camera_distance_ × tan(fov/2) so toggling looks like a
-    // smooth swap rather than a jump in apparent size.
-    bool  projection_ortho_ = false;
+    // Camera state aliases (storage in core_).
+    float (&camera_target_)[3];
+    float& camera_distance_;
+    bool&  projection_ortho_;
 
     // Fly / FPS-mode state. Mirrors GL ViewportWindow::CameraMode::Fps.
     // While fps_mode_ is true: cursor is hidden, mouse-look uses raw
@@ -928,11 +921,11 @@ private:
     // mouseMoveEvent so mid-drag modifier changes don't switch axes.
     enum class NavDrag : uint8_t { Inactive, Orbit, Pan };
     NavDrag nav_drag_kind_ = NavDrag::Inactive;
-    float camera_yaw_deg_   = 45.0f;
-    float camera_pitch_deg_ = 30.0f;
-    float camera_fov_y_deg_ = 45.0f;
-    float camera_near_      = 0.1f;
-    float camera_far_       = 10000.0f;
+    float& camera_yaw_deg_;
+    float& camera_pitch_deg_;
+    float& camera_fov_y_deg_;
+    float& camera_near_;
+    float& camera_far_;
 
     // Contribution-cull thresholds. Still-frame uses min_pixel_radius_;
     // when the camera changed since last frame, the bigger motion threshold