refactor: move common/shaders/ to src/shaders/

Relocates shared WGSL shaders under src/ where all source code lives,
eliminating the top-level common/ directory.

- Update asset references in workspaces/main/assets.txt and workspaces/test/assets.txt
- Update docs: PROJECT_CONTEXT.md, ARCHITECTURE.md, WORKSPACE_SYSTEM.md, SHADER_REUSE_INVESTIGATION.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/shaders/ray_box.wgsl b/src/shaders/ray_box.wgsl
new file mode 100644
index 0000000..37b9d6a
--- /dev/null
+++ b/src/shaders/ray_box.wgsl
@@ -0,0 +1,16 @@
+struct RayBounds {
+    t_entry: f32,
+    t_exit: f32,
+    hit: bool,
+};
+
+fn ray_box_intersection(ro: vec3f, rd: vec3f, extent: vec3f) -> RayBounds {
+    let inv_rd = 1.0 / rd;
+    let t0 = (-extent - ro) * inv_rd;
+    let t1 = (extent - ro) * inv_rd;
+    let tmin_vec = min(t0, t1);
+    let tmax_vec = max(t0, t1);
+    let t_entry = max(0.0, max(tmin_vec.x, max(tmin_vec.y, tmin_vec.z)));
+    let t_exit = min(tmax_vec.x, min(tmax_vec.y, tmax_vec.z));
+    return RayBounds(t_entry, t_exit, t_entry <= t_exit);
+}