[krisnye]

Adds order to System.render, so one draw covers several archetypes in an index's order. A 2D editor needs this to blend translucent shapes, images and text back to front.

Contract change

• System.render's declaration takes order?: Index<{ sorted: true; key: Component.Key[] }>, constrained as System.create's order is. A hash index or a value that isn't an index is a type error, and throws at creation.
• With order, the body's tables holds exactly one table, even when nothing matches. Its count is every matching row across archetypes, with has/not applied, and its bind makes instance i the i-th of them in index order.
• Shaders are unchanged: the accessors keep fn name(row: u32), and row is the position in the order. Gpu.wgsl emits a different record and an ecs_address helper for an ordered system. Its output for unordered systems is unchanged byte for byte.
• A run fails in its report when a matching archetype holds more rows than fit beside its slot in 32 bits: 2^31 with up to two matching archetypes, 2^30 with up to four, and so on.
• The package version is 0.2.0. This supersedes ecs: version 0.1.1 #219: merge it instead, or merge ecs: version 0.1.1 #219 first and I'll rebase.

Performance (chromium, 50K entities in two archetypes)

	Ordered	Unordered, as two tables
Unchanged frame	0.030–0.036 ms	0.045–0.049 ms
One key changed	0.268–0.294 ms	0.042–0.050 ms

An unchanged frame writes nothing to the GPU and allocates nothing. A changed key rebuilds the order list (0.17 ms) and writes its 200 KB (0.07 ms).

Tests

• render-order.browser.test.ts, covering:
  • two archetypes interleaved in depth;
  • has/not;
  • a despawn that moves a row, a spawn, a key change, and a hidden entity shown;
  • exactly one table, even when nothing matches;
  • writes only on change;
  • the ordered WGSL compiling.
• Type tests for sorted, hash, unknown and non-index orders.
• pnpm run build and pnpm test in packages/ecs pass: 134 files and 1010 tests.

🤖 Generated with Claude Code