Add structured talent mechanics

docs/DESIGN_SYSTEM.md

@@ -511,6 +511,17 @@ text is operationally useful. Use compact wrapping description cells rather
 than replacing meaningful data with a generic “configured” label; retain an
 explicit textual missing state when a tier has no rendered description.
 
+Talent mechanics are structured metadata, not free-form prose. Present optional
+cooldown, duration, and maximum-stack inputs together in a compact three-column
+mechanics strip that collapses to one column on narrow screens. Description
+templates use numbered expressions (`{1}`, `{2}`) for tiered attribute effects
+and named expressions (`{duration}`, `{max_stacks}`) for shared mechanics.
+Named expressions are valid only when their corresponding value is defined.
+Cooldown is never embedded in the description: render it consistently as
+`Talent Cooldown: [value] seconds` beneath the talent identity or description.
+Do not imply an absent mechanic with a zero value; show no cooldown line and
+leave optional editor fields explicitly marked as not defined.
+
 ### Registry pagination
 
 Every primary ISAC registry uses server-side pagination. The shared control