Add formal enemies, remaining formal partners and synthesized UI SFX

- UI SFX v3: procedurally synthesized one-shots (Tools/synth_ui_sfx.py) wired to
  buttons, rewards, errors and red dots via UiSfx, gated by the SFX setting.
- Five formal enemies (Hornlet, Dashlet, Shellhorn, HornCaptain, GreatHorn):
  Hunyuan 50k -> 2000-tri XPbr, DGXA TokenRig, Idle/Walk/Attack, nested per type
  in PrototypeArena; PrototypeBattle.Enemy gains presentation-only Moving/Strikes.
- Formal partners for all ten pets in the arena and portraits, including new
  VineSprite, ThunderLeopard and TideWhale.
- Pipeline fixes: reject local TokenRig fallback, drop loose mesh islands,
  configurable Unity run_script timeout, companion static stage.
- Also includes concurrent work from another tool in this working tree
  (FlameLion, enemy combat FX, challenge mode, home explorer, server updates).
- Resources registered in Doc/ResDesc_*.md; verified on isolated :18081.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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