Remediation: Implement shared common/shaders/ directory

Eliminates 36 duplicate shader files across workspaces.

Structure:
- common/shaders/{math,render,compute}/ - Shared utilities (20 files)
- workspaces/*/shaders/ - Workspace-specific only

Changes:
- Created common/shaders/ with math, render, compute subdirectories
- Moved 20 common shaders from workspaces to common/
- Removed duplicates from test workspace
- Updated assets.txt: ../../common/shaders/ references
- Enhanced asset_packer.cc: filesystem path normalization for ../ resolution

Implementation: Option 1 from SHADER_REUSE_INVESTIGATION.md
- Single source of truth for common code
- Workspace references via relative paths
- Path normalization in asset packer

handoff(Claude): Common shader directory implemented

1 files changed, 36 insertions, 0 deletions

diff --git a/common/shaders/math/common_utils.wgsl b/common/shaders/math/common_utils.wgsl
new file mode 100644
index 0000000..7131216
--- /dev/null
+++ b/common/shaders/math/common_utils.wgsl
@@ -0,0 +1,36 @@
+// Common utility functions for WGSL shaders.
+// Reduces duplication across renderer_3d, mesh_render, etc.
+
+// Constants
+const PI: f32 = 3.14159265359;
+const TAU: f32 = 6.28318530718;
+
+// Transform normal from local to world space using inverse model matrix
+fn transform_normal(inv_model: mat4x4<f32>, normal_local: vec3<f32>) -> vec3<f32> {
+    let normal_matrix = mat3x3<f32>(inv_model[0].xyz, inv_model[1].xyz, inv_model[2].xyz);
+    return normalize(normal_matrix * normal_local);
+}
+
+// Spherical UV mapping (sphere or any radial surface)
+// Returns UV in [0,1] range
+fn spherical_uv(p: vec3<f32>) -> vec2<f32> {
+    let u = atan2(p.x, p.z) / TAU + 0.5;
+    let v = acos(clamp(p.y / length(p), -1.0, 1.0)) / PI;
+    return vec2<f32>(u, v);
+}
+
+// Spherical UV from direction vector (for skybox, etc.)
+fn spherical_uv_from_dir(dir: vec3<f32>) -> vec2<f32> {
+    let u = atan2(dir.z, dir.x) / TAU + 0.5;
+    let v = asin(clamp(dir.y, -1.0, 1.0)) / PI + 0.5;
+    return vec2<f32>(u, v);
+}
+
+// Grid pattern for procedural texturing (checkerboard-like)
+fn grid_pattern(uv: vec2<f32>) -> f32 {
+    let grid = 0.5 + 0.5 * sin(uv.x * PI) * sin(uv.y * PI);
+    return smoothstep(0.45, 0.55, grid);
+}
+
+// NOTE: calc_sdf_normal_bumped() removed - too specialized, depends on get_dist()
+// from scene_query snippets. Keep bump mapping code inline in shaders that use it.