fix(wasm): make the web build actually run in the browser

With the wasm bundle building, get it rendering in a browser:

- Enable iced `webgl` so wgpu uses WebGL2 where WebGPU is absent
  (e.g. Firefox by default), and `fira-sans` so UI text has an
  embedded font (the web has no system fonts) — without it every
  label was blank.
- Replace `std::time::Instant` with `iced::time::Instant` (web-safe);
  `Instant::now()` panics ("time not implemented") on wasm and crashed
  at boot via the command line.
- Skip the batched-hatch pipeline on wasm: its bind group needs
  vertex-stage storage buffers, which WebGL2 lacks (validation error
  on "New drawing"). Fields become Option; upload/draw guard on them.
  Hatches don't draw on the web for now; everything else does.
- Fix the trunk feature flag (`data-cargo-no-default-features`) and
  ignore the `dist/` build output.

Native build + 75 tests unchanged.

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

Trunk.toml

@@ -8,6 +8,9 @@
 
 [build]
 target = "index.html"
+# Note: the `solid3d` feature is disabled via `data-cargo-no-default-features`
+# on the rust <link> in index.html (truck-meshalgo → lzma-sys C deps cannot
+# cross-compile to wasm).
 
 [serve]
 # Cross-origin isolation headers enable SharedArrayBuffer, which wasm threads