feat: add Person, procedural characters with styles and skins

[anistark]

• New person component: a seeded, clothed, articulated human figure with kind role presets (villager, merchant, guard, sailor, farmer, noble, scholar, traveler), gender/age/height/build silhouettes, hair, facial hair, outfits, hats, accessories, and poses
• style templates set the whole look: anime (default, big lit eyes, ~6-head proportions) or realistic (canonical 7.5-head figure)
• skin swaps a full cosmetic loadout (clothes, colors, headwear, accessories) as one JSON prop; nine named presets ship as PERSON_SKINS, from festival to pirate
• Figures breathe, blink, shift their weight, and turn their head to watch you; detail drops to a cheap silhouette past ~18 units
• physics={false} turns one into a bare visual, which is how Player gets its new third-person body
• Trait precedence is explicit prop > skin > kind > seed, so <Person seed={3} /> is a complete villager and every prop narrows it

For devs:

• Geometry is lathe profiles (tapered limbs, one-piece elliptical torso), built in one useMemo and animated via joint groups in useFrame; one capsule collider
• New styles are one StyleSpec record; skins are PersonSkin bundles resolved by name or object
• Registered in index.ts, registry.ts, registry/registry.json (category character); manifest and component doc regenerated; gallery preview + SEEDED entry
• The docs library world places a librarian and a traveler and hands Player a Person avatar