refactor: remove the legacy full view_proj (CPU cull now relative-to-eye)

The GPU draws exclusively via the rotation-only `view_rot` + eye double-
single; the full view-projection survived only to project AABBs in the
CPU frustum-cull / scissor / LOD passes. Migrate those to the same
relative-to-eye math (project `point - eye` through `view_rot`) — pixel-
equivalent but precise at UTM scale — then drop the dead uniform:

- pipeline cull/scissor/LOD helpers take (view_rot, eye) instead of the
  full view_proj; render.rs reconstructs eye from the uniform's
  eye_high/eye_low and passes the cropped view_rot.
- Remove the `view_proj` field from the shared Uniforms struct and all six
  shader structs that only declared it for layout (none read it), and
  delete Camera::view_proj(). The struct shrinks by one mat4 on both
  sides, keeping the Rust / WGSL layouts in lock-step.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/shaders/face3d.wgsl

@@ -5,7 +5,6 @@
 //   color     [f32; 4]   offset 12   16 B
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch.wgsl

@@ -13,7 +13,6 @@
 // ── Group 0: frame uniforms (shared) ──────────────────────────────────────
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/hatch_batched.wgsl

@@ -18,7 +18,6 @@
 // ── Group 0: shared frame uniforms (matches hatch.wgsl) ──────────────────
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/image.wgsl

@@ -4,7 +4,6 @@
 // ── Bind group 0: shared projection uniforms ─────────────────────────────────
 // Must match the shared `Uniforms` struct (scene::pipeline::uniforms, 112 B).
 struct Uniforms {
-    view_proj:          mat4x4<f32>,
     viewport_size:      vec2<f32>,
     world_per_pixel:    f32,
     lwdisplay_enable:   f32,

src/shaders/mesh.wgsl

@@ -10,7 +10,6 @@
 //     flat shade (FlatShaded).
 
 struct Uniforms {
-    view_proj:           mat4x4<f32>,
     viewport_size:       vec2<f32>,
     world_per_pixel:     f32,
     lwdisplay_enable:    f32,

src/shaders/wire.wgsl

@@ -14,7 +14,6 @@
 //   • pat0/pat1 encode up to 8 elements: positive=dash, negative=gap.
 
 struct Uniforms {
-    view_proj:        mat4x4<f32>,
     viewport_size:    vec2<f32>,
     world_per_pixel:  f32,
     // LWDISPLAY toggle: 0.0 = force 1 px (half_width 0.5), 1.0 = use the