chore: silence native and wasm build warnings

Gate target-specific code so neither build warns about the other's items:
native-only helpers (view, window icon, file dialogs, file association, plugin
host/guard/registry, self-update) are cfg'd to non-wasm; the wasm-only font
fallback (script_of / cjk_lang / request) is cfg'd to wasm. Drop an unused mut,
allow the few genuinely-conditional dead items (mesh_click_hit, GPU layout
helpers, parity stubs), and gate the embedded PlotSettings-unrelated dead
constants. Both targets now build clean (only the unavoidable nom/quick-xml
future-incompat dependency notice remains).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/scene/convert/solid3d_tess.rs

@@ -385,6 +385,7 @@ pub(crate) fn collect_loop_polygon(
 
 /// All loops of a face: the outer boundary first, then any inner hole loops.
 /// Each loop is returned as an ordered 3-D polygon (≥ 3 points).
+#[cfg(feature = "solid3d")]
 pub(crate) fn collect_face_loops(
     sat: &SatDocument,
     face: &SatFace,

src/scene/convert/truck_tess.rs

@@ -19,6 +19,7 @@ use truck_polymesh::PolygonMesh;
 // Chord-height tolerance used for adaptive curve sampling (world units).
 const CURVE_TOL: f64 = 0.005;
 // Triangle mesh tolerance (world units).
+#[allow(dead_code)]
 pub const MESH_TOL: f64 = 0.01;
 
 // ── Zoom-adaptive curve tolerance override ────────────────────────────────