feat(rules): the race, calling, skill and attribute tables

Mechanics are rules and live in code, beside Luck and Currency. The skill pools
are new — the races/classes spec said only 'the stat-appropriate slice' and never
enumerated them; each pool is larger than its pick count so the choice is real.

The dwarf's +2 vs poison is exposed separately from save() rather than folded
into it: baking a conditional into a flat number is how a sheet starts lying.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QYa9u7Kdxv5gX4AnwWexy8

client/scripts/rules/attributes.gd

@@ -0,0 +1,15 @@
+class_name Attributes
+extends RefCounted
+## The five attribute rows and the one modifier formula. LCK is deliberately NOT
+## here — it is never an attribute row, never a save, never a skill (§7). It lives
+## in GameState.luck.
+
+const IDS := ["str", "dex", "con", "fth", "mag"]
+
+
+static func exists(id: String) -> bool:
+	return id in IDS
+
+
+static func modifier(score: int) -> int:
+	return floori((score - 10) / 2.0)