feat(mod): Stage 3 (continued 2) — entity + block + Sodium contract mixins

Per mod/docs/optimize-layer-design.md Stage 3 (continued). This batch
implements the Stage 1 mixin-contract interfaces on their target MC classes
so CachedName, StateEntity, TickCached, CachedLight, CachedValidity and
CachedStack actually get used. Seven new mixin'ов; no new helpers (the
helpers were all written in Stage 1 already).

Entity-contract mixins (mixins/optimize/entity/):
- EntityNameMixin: implements CachedName on Entity — adds the per-tick
  cached name-tag fields (Component + tick). Vanilla Entity.getDisplayName()
  rebuilds the team prefix + name + suffix on every call.
- EntityRenderStateEntityMixin: implements StateEntity on EntityRenderState —
  adds the back-reference field to the source Entity. Render-states are
  rebuilt every frame so they can't keep their own pointer; this is captured
  by EntityRendererStateMixin.
- EntityRendererStateMixin: Inject at RETURN on EntityRenderer.createRenderState
  — captures the source Entity on the freshly-built state via the StateEntity
  contract. ZakoOpt used @ModifyReturnValue; we use plain @Inject because the
  MixinExtras ModifyReturnValue transformer is more fragile across MC versions.
- EntityRendererNameMixin: WrapOperation on EntityRenderer.getNameTag's
  Entity.getDisplayName call — caches by game tick so the per-frame cost is
  one identity check + read instead of a full Component rebuild.
- SodiumEntityRendererMixin: WrapOperation on Sodium EntityRenderer.renderCuboid's
  MemoryStack.stackPush — uses CachedStack (Stage 1) to skip the ThreadLocal
  lookup on the render thread. Registered as optional via LoVisualMixinPlugin
  (only applied when Sodium is loaded); remap = false because the target is
  a Sodium class, not a Mojang one.

BlockEntity-contract mixins (mixins/optimize/block/):
- BlockEntityMixin: implements TickCached + CachedLight + CachedValidity on
  BlockEntity — adds the per-tick cache slot, per-tick block-light lookups
  (single + pair for double-chests), per-tick should-render distance check,
  and per-state validity cache. All four are read by the (Stage 3, future)
  ChestRendererMixin / BlockEntityRenderStateMixin / BlockEntityRenderDispatcherMixin.
- BaseSpawnerMixin: implements TickCached on BaseSpawner — adds the per-tick
  cache slot that SpawnerCache (Stage 1) reads back.

Folder limit (≤4 .java per folder):
- mixins/optimize/entity/ hit 6 files after this batch — split into
  mixins/optimize/entity/renderer/ for EntityRendererStateMixin +
  EntityRendererNameMixin (the two that target EntityRenderer rather than
  Entity/EntityRenderState directly). The other 4 stay in entity/.

lovisual.mixins.json: seven new entries in the 'client' array, alphabetical:
  optimize.block.BaseSpawnerMixin
  optimize.block.BlockEntityMixin
  optimize.entity.EntityNameMixin
  optimize.entity.EntityRenderStateEntityMixin
  optimize.entity.SodiumEntityRendererMixin
  optimize.entity.renderer.EntityRendererNameMixin
  optimize.entity.renderer.EntityRendererStateMixin

LoVisualMixinPlugin: added SodiumEntityRendererMixin to OPTIONAL_SODIUM_MIXINS
so the mixin is only applied when Sodium is loaded (matches the existing
convention for sodium.* mixins).

Tests: no new tests in this batch (the new mixins are pure side-effect
field-bags — they don't have unit-testable logic). Existing suite still green.
Total: 866 tests, 0 failures. checkFolderLimit: OK (0 папок >4).

mod/src/main/java/dev/loki/lovisual/mixins/LoVisualMixinPlugin.java

@@ -21,7 +21,8 @@ public final class LoVisualMixinPlugin implements IMixinConfigPlugin {
             "dev.loki.lovisual.mixins.sodium.terrain.SodiumShaderChunkRendererMixin",
             "dev.loki.lovisual.mixins.sodium.vertex.SodiumVertexConsumerTrackerMixin",
             "dev.loki.lovisual.mixins.sodium.placement.SodiumPlaceCullMixin",
-            "dev.loki.lovisual.mixins.sodium.placement.SodiumPlaceHideMixin"
+            "dev.loki.lovisual.mixins.sodium.placement.SodiumPlaceHideMixin",
+            "dev.loki.lovisual.mixins.optimize.entity.SodiumEntityRendererMixin"
     );
     private static final Set<String> OPTIONAL_IRIS_MIXINS = Set.of(
             "dev.loki.lovisual.mixins.iris.render.IrisCommonUniformsMixin",