"""Validate the world seeds the way the C++ loaders do at boot — but headless, in
under a second, so a biome/flora edit can be checked before a 20-minute cook.

Cross-checks  data/seeds/biomes.yml  <->  world_templates.yml  <->  flora.yml
against the authoritative asset resolution in
game/Source/AgeOfEons/Private/World/AoEFlora.cpp.

ERRORS are the things that make a real boot FAIL LOUD (AoEWorldTemplateLibrary /
FAoEFloraManifest::ValidateAssets Fatal/checkf):
  * a biome_set names a biome absent from biomes.yml
  * a biome exists but its `eras:` omits the era that names it
  * an era's biome_set has no marine/freshwater biome (oceans/lakes can't land)
  * a flora palette names an asset slug that resolves to NOTHING (no on-disk
    external_assets/flora/<slug>/ folder AND not in ExplicitMeshPaths())

WARNINGS degrade gracefully (the world still boots, it just looks poorer):
  * a biome in a biome_set has no flora palette -> default scatter (bare-ish)
  * an era has no flora block at all
  * a flora palette targets a biome the era's biome_set doesn't include (dead data)

Exit code: 1 if any ERROR, else 0.  Run:  python tools/validate_world_seeds.py
"""
import re
import sys