feat(draworder): cross-type draw order + context menu

DRAWORDER now affects rendering immediately (bump geometry epoch so the
sort cache rebuilds) and front/back anchor to the block's full effective
sort range instead of only existing table entries, so bring-to-front
actually lands on top. The render fallback sorts table-absent entities by
their own handle.

Draw order now applies across entity types, not just within a type. A
per-entity draw-order rank (SortEntitiesTable override or own handle,
ranked per block) is encoded as a small signed clip-z bias in the wire,
hatch, image, and 3DFACE pipelines. The shared LessEqual depth buffer then
orders fills, lines, rasters and 2D solids against each other regardless of
pass order — without touching model coordinates. 3D meshes keep real
geometric depth; wipeouts stay always-on-top.

Adds a Draw Order submenu to the viewport context menu (Bring to Front,
Send to Back, Bring Above/Send Under Object). The above/under items run an
interactive reference-object pick, then reorder the captured selection.

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

src/shaders/hatch_batched.wgsl

@@ -45,9 +45,14 @@ struct HatchInstance {
     boundary_count:  u32,
     family_offset:   u32,
     family_count:    u32,
-    _pad0:           vec2<u32>,
+    draw_depth:      f32,          // signed (-1,1) draw-order bias; 0 = neutral
+    _pad0:           u32,
 }
 
+// Draw-order depth bias (see wire.wgsl). Higher draw_depth → smaller z →
+// drawn on top, ordering this fill against other entity types.
+const DRAW_ORDER_BIAS: f32 = 0.001;
+
 struct LineFamily {
     cos_a:       f32,
     sin_a:       f32,
@@ -122,6 +127,7 @@ fn corner_xy(c: u32, aabb: vec4<f32>) -> vec2<f32> {
                           local.y + inst.world_origin.y,
                           0.0);
     o.clip = u.view_proj * vec4<f32>(world, 1.0);
+    o.clip.z = o.clip.z - inst.draw_depth * DRAW_ORDER_BIAS * o.clip.w;
     o.xz = local;
     o.instance_index = v.instance_index;
     return o;