GEN-1: add vitest suite (worked example, SpSp renorm, wildcards) + erasable-enum fix

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

gerbil-manager-web/src/genetics/warnings.ts

@@ -1,13 +1,19 @@
 /**
  * Warning codes emitted by the genetics engine. The engine is language-neutral:
  * it emits CODES only. German texts are mapped in de.ts (UI layer).
+ *
+ * Modelled as a const object (not a TS `enum`) because the project's tsconfig
+ * enables `erasableSyntaxOnly`.
  */
-export enum GeneticsWarningCode {
+export const GeneticsWarningCode = {
   /** Schecke × Schecke: SpSp embryos die in utero; ~25% fewer live young. */
-  ScheckeLethal = 'SCHECKE_LETHAL',
+  ScheckeLethal: 'SCHECKE_LETHAL',
   /** Rex × Rex: ReRe is semi-lethal; reduced viability of homozygous young. */
-  RexSemiLethal = 'REX_SEMI_LETHAL',
-}
+  RexSemiLethal: 'REX_SEMI_LETHAL',
+} as const
+
+export type GeneticsWarningCode =
+  (typeof GeneticsWarningCode)[keyof typeof GeneticsWarningCode]
 
 export interface GeneticsWarning {
   readonly code: GeneticsWarningCode