render entities from vanilla client models, add items, displays and leashes

- dump entity models straight from the unobfuscated client jar
  (tools/VanillaModelDump.java, tools/update-vanilla-models.sh): models posed
  by vanilla setupAnim, baby/variant/layer models, renderer transforms,
  default textures, pose variants (sitting, holding items, illager arms)
  and all layer definitions; the old CEM template is only a fallback now
- fix adult zombies captured as babies, zero-thickness planes (wings,
  fins) and back faces in the entity intersector
- held items, head items (pumpkins, skulls), shields, elytra, saddles and
  body equipment for every mount, armor following the pose
- block/item/text display entities, dropped items, falling blocks, primed
  TNT, minecart contents, block entities inside displays, leash ropes
- item models resolved from the 26.x item definitions with display
  transforms; generated items extruded like vanilla
- bundle the vanilla font definitions as fallback so sign/text rendering
  works with packs that lack font/*.json
- one failing entity no longer aborts the whole photo
- edge-case test plugin (tools/edgecase-plugin) and offline harnesses

tools/update-cem-models.sh

@@ -4,10 +4,9 @@
 # Source: the CEM Template Loader data (Ewan Howell / wynem) — vanilla Java entity models as JSON,
 # already correctly posed. These ultimately mirror Mojang's hardcoded Java EntityModel classes.
 #
-# Most future-proof alternative for a NEW Minecraft version (sourced straight from the game):
-#   1. Install the JsonEM mod (Fabric), set dump_models=true in .minecraft/config/jsonem.properties
-#   2. Launch the game once -> models dumped to .minecraft/jsonem_dump
-#   (a small format-adapter would be needed; the CEM source below covers vanilla until then.)
+# NOTE: this set is now only the FALLBACK (rest-pose geometry) + the block-entity models (chests, signs,
+# heads, banners, armor_layer_*). Mob models come from the vanilla client dump — regenerate that with
+# tools/update-vanilla-models.sh <version> on every Minecraft update.
 #
 # Usage:  tools/update-cem-models.sh           # update if newer
 #         tools/update-cem-models.sh --force   # always overwrite