refactor(render): drop dead camera_pos from the shared uniform

No GPU pipeline reads camera_pos any more — lighting and all transforms
moved to the relative-to-eye path (view_rot + eye_high/eye_low). Remove
the field from the shared Uniforms and every shader struct, plus the now
unused Camera::position_vec4. view_proj stays: the CPU frustum-cull /
scissor / LOD passes still project offset-relative AABBs with it (it is
no longer part of any GPU draw).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/scene/pipeline/uniforms.rs

@@ -4,8 +4,11 @@ use iced::Rectangle;
 #[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
 #[repr(C)]
 pub struct Uniforms {
+    /// Full view-projection (with translation) — GPU rendering no longer uses
+    /// this; it remains for the CPU-side frustum-cull / scissor / LOD passes
+    /// that project offset-relative AABBs to screen. The GPU draws via the
+    /// relative-to-eye `view_rot` + `eye_high`/`eye_low` below.
     pub view_proj: glam::Mat4,
-    pub camera_pos: glam::Vec4,
     pub viewport_size: [f32; 2],
     /// World units per screen pixel at the current zoom. Used by the
     /// hatch shader to substitute solid fill when pattern line spacing
@@ -52,7 +55,6 @@ impl Uniforms {
         let (eye_high, eye_low) = camera.eye_high_low();
         Self {
             view_proj: camera.view_proj(bounds),
-            camera_pos: camera.position_vec4(),
             viewport_size: [bounds.width, bounds.height],
             world_per_pixel,
             lwdisplay_enable: if lwdisplay_enable { 1.0 } else { 0.0 },

src/scene/view/camera.rs

@@ -228,9 +228,6 @@ impl Camera {
         }
     }
 
-    pub fn position_vec4(&self) -> glam::Vec4 {
-        glam::Vec4::from((self.eye(), 0.0))
-    }
 
     // ── ViewCube rotation matrix ───────────────────────────────────────────
 

src/shaders/face3d.wgsl

@@ -6,7 +6,6 @@
 
 struct Uniforms {
     view_proj:           mat4x4<f32>,
-    camera_pos:          vec4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch.wgsl

@@ -14,7 +14,6 @@
 
 struct Uniforms {
     view_proj:           mat4x4<f32>,
-    camera_pos:          vec4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch_batched.wgsl

@@ -19,7 +19,6 @@
 
 struct Uniforms {
     view_proj:           mat4x4<f32>,
-    camera_pos:          vec4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/image.wgsl

@@ -5,7 +5,6 @@
 // Must match the shared `Uniforms` struct (scene::pipeline::uniforms, 112 B).
 struct Uniforms {
     view_proj:          mat4x4<f32>,
-    camera_pos:         vec4<f32>,
     viewport_size:      vec2<f32>,
     world_per_pixel:    f32,
     lwdisplay_enable:   f32,

src/shaders/mesh.wgsl

@@ -11,7 +11,6 @@
 
 struct Uniforms {
     view_proj:           mat4x4<f32>,
-    camera_pos:          vec4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/wire.wgsl

@@ -15,7 +15,6 @@
 
 struct Uniforms {
     view_proj:        mat4x4<f32>,
-    camera_pos:       vec4<f32>,
     viewport_size:    vec2<f32>,
     world_per_pixel:  f32,
     // LWDISPLAY toggle: 0.0 = force 1 px (half_width 0.5), 1.0 = use the