Add boss team match playstyle rule

When enabled, the sticky boss banner shows the next boss's team size
as a hint for players who voluntarily match the boss's party count.
Handles variant boss teams by using the auto-detected starter variant.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/types/rules.ts

@@ -9,6 +9,7 @@ export interface NuzlockeRules {
   // Playstyle (informational, for stats/categorization)
   hardcoreMode: boolean
   setModeOnly: boolean
+  bossTeamMatch: boolean
 
   // Variant (changes which Pokemon can appear)
   egglocke: boolean
@@ -27,6 +28,7 @@ export const DEFAULT_RULES: NuzlockeRules = {
   // Playstyle - off by default
   hardcoreMode: false,
   setModeOnly: false,
+  bossTeamMatch: false,
 
   // Variant - off by default
   egglocke: false,
@@ -93,6 +95,13 @@ export const RULE_DEFINITIONS: RuleDefinition[] = [
       'The game must be played in "Set" battle style, meaning you cannot switch Pokémon after knocking out an opponent.',
     category: 'playstyle',
   },
+  {
+    key: 'bossTeamMatch',
+    name: 'Boss Team Match',
+    description:
+      'Limit your active party to the same number of Pokémon as the boss you are challenging.',
+    category: 'playstyle',
+  },
 
   // Variant
   {