feat(web): render hatches on WebGL2 via a texture-backed renderer

WebGL2 has no vertex/fragment storage buffers, so the batched storage-buffer
hatch renderer (hatch_gpu) is disabled on wasm and real hatch fills never
rendered on the web build — the pick highlighted the boundary and the command
then appeared to cancel (issue #204).

Add a wasm-only per-hatch renderer (hatch_web_gpu + hatch_web.wgsl) that packs
the variable-length boundary / family / dash arrays into one RGBA32F data
texture read with textureLoad, instead of the fixed-size uniforms of the
wipeout path. This removes the MAX_FAMILIES (16) / MAX_HATCH_BOUNDARY_VERTS
(1024) / MAX_DASHES (128) caps, so every hatch — solid, gradient, and
arbitrarily complex line patterns — renders on the web. The fill algorithm
(in_polygon, per-family line/dash/dot, gradient, LOD, double-single vertex
transform) is identical to the desktop path; only the array ACCESS changes.
Pattern phase is anchored at world_origin with the boundary stored raw, and
scale / gradient-range clamped, to match the desktop batched renderer exactly.

Native (hatch_gpu + hatch.wgsl) and the wipeout mask renderer are untouched;
the new module and pipeline are gated on target_arch = "wasm32".

Also silence the resulting (and pre-existing) wasm-only dead-code warnings for
native-only paths so both the native and web builds compile clean.

Closes #204.

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

src/scene/view/render.rs

@@ -319,10 +319,10 @@ impl shader::Primitive for Primitive {
                 let sel_changed = vp.selected_sig != inner.cached_epoch.2;
                 if geo_changed || sel_changed {
                     if fill_mode {
-                        inner.upload_hatches(device, &vp.hatches[..]);
+                        inner.upload_hatches(device, queue, &vp.hatches[..]);
                         inner.upload_wipeouts(device, &vp.wipeout_hatches[..]);
                     } else {
-                        inner.upload_hatches(device, &[]);
+                        inner.upload_hatches(device, queue, &[]);
                         inner.upload_wipeouts(device, &[]);
                     }
                 }