Give every NPC a race and class, resolved at spawn time

NPCs can now optionally specify race and class in their TOML. When
omitted, race is randomly selected from non-hidden races and class is
determined by the race's default_class or picked randomly from
compatible non-hidden classes. Race/class are re-rolled on each
respawn for NPCs without fixed values, so killing the barkeep may
bring back a different race next time.

New hidden content (excluded from character creation):
- Beast race: for animals (rats, etc.) with feral stats and no
  equipment slots
- Peasant class: weak default for humanoid NPCs
- Creature class: default for beasts/animals

Existing races gain default_class fields (humanoids → peasant,
beast → creature, dragon → random compatible). Look and examine
commands now display NPC race and class.

Made-with: Cursor

world/classes/creature.toml

@@ -0,0 +1,13 @@
+name = "Creature"
+description = "A wild thing that fights on instinct alone."
+hidden = true
+
+[base_stats]
+max_hp = 30
+attack = 6
+defense = 2
+
+[growth]
+hp_per_level = 4
+attack_per_level = 2
+defense_per_level = 0

world/classes/peasant.toml

@@ -0,0 +1,13 @@
+name = "Peasant"
+description = "A common folk with no particular training or aptitude for adventure."
+hidden = true
+
+[base_stats]
+max_hp = 50
+attack = 4
+defense = 4
+
+[growth]
+hp_per_level = 5
+attack_per_level = 1
+defense_per_level = 1