feat(xanthous): Fistfighting builds knuckle calluses

2000 ticks after the character damages their fists by hitting something,
the character now develops calluses on their fists (scaled by *how*
damaged they've become) that reduce the chance of them receiving
additional damage from hitting things - up to a max of 5, which
prevents *all* damage from fistfighting.

This is all tracked in a new "Knuckles" struct in a new "Body" struct on
the character datatype, which manages stepping itself forward as part of
the Brain impl on the character.

Change-Id: Ica269f16fb340fb25900d2c77fbad32f10c00be2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3222
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/grfn/xanthous/xanthous.cabal

@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 715e0ab333afb8723ffec128cf69c065f6f018e9622d65c45d404e5084852f54
+-- hash: b39d4dd906804ca42f8965c2dbe519434e80622fef7fafce1dca0d211a1c6663
 
 name:           xanthous
 version:        0.1.0.0
@@ -355,6 +355,7 @@ test-suite test
       Xanthous.Data.MemoSpec
       Xanthous.Data.NestedMapSpec
       Xanthous.DataSpec
+      Xanthous.Entities.CharacterSpec
       Xanthous.Entities.RawsSpec
       Xanthous.Game.StateSpec
       Xanthous.GameSpec