Add conditional boss battle teams (variant teams by condition)

Wire up the existing condition_label column on boss_pokemon to support
variant teams throughout the UI. Boss battles can now have multiple team
configurations based on conditions (e.g., starter choice in Gen 1).

- Add condition_label to BossPokemonInput schema (frontend + backend bulk import)
- Rewrite BossTeamEditor with variant tabs (Default + named conditions)
- Add variant pill selector to BossDefeatModal team preview
- Add BossTeamPreview component to RunEncounters boss cards
- Fix MissingGreenlet error in set_boss_team via session.expunge_all()
- Fix PokemonSelector state bleed between tabs via composite React key
- Add Alembic migration for condition_label column

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

frontend/src/pages/RunEncounters.tsx

@@ -26,6 +26,7 @@ import type {
   EncounterStatus,
   CreateEncounterInput,
   BossBattle,
+  BossPokemon,
 } from '../types'
 
 const statusStyles: Record<RunStatus, string> = {
@@ -145,6 +146,67 @@ function countDistinctZones(group: RouteWithChildren): number {
   return zones.size
 }
 
+function BossTeamPreview({ pokemon }: { pokemon: BossPokemon[] }) {
+  const variantLabels = useMemo(() => {
+    const labels = new Set<string>()
+    for (const bp of pokemon) {
+      if (bp.conditionLabel) labels.add(bp.conditionLabel)
+    }
+    return [...labels].sort()
+  }, [pokemon])
+
+  const hasVariants = variantLabels.length > 0
+  const [selectedVariant, setSelectedVariant] = useState<string | null>(
+    hasVariants ? variantLabels[0] : null,
+  )
+
+  const displayed = useMemo(() => {
+    if (!hasVariants) return pokemon
+    return pokemon.filter(
+      (bp) => bp.conditionLabel === selectedVariant || bp.conditionLabel === null,
+    )
+  }, [pokemon, hasVariants, selectedVariant])
+
+  return (
+    <div className="mt-2">
+      {hasVariants && (
+        <div className="flex gap-1 mb-2 flex-wrap">
+          {variantLabels.map((label) => (
+            <button
+              key={label}
+              type="button"
+              onClick={() => setSelectedVariant(label)}
+              className={`px-2 py-0.5 text-xs font-medium rounded-full transition-colors ${
+                selectedVariant === label
+                  ? 'bg-blue-600 text-white'
+                  : 'bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-300 hover:bg-gray-200 dark:hover:bg-gray-600'
+              }`}
+            >
+              {label}
+            </button>
+          ))}
+        </div>
+      )}
+      <div className="flex gap-2 flex-wrap">
+        {[...displayed]
+          .sort((a, b) => a.order - b.order)
+          .map((bp) => (
+            <div key={bp.id} className="flex items-center gap-1">
+              {bp.pokemon.spriteUrl ? (
+                <img src={bp.pokemon.spriteUrl} alt={bp.pokemon.name} className="w-20 h-20" />
+              ) : (
+                <div className="w-20 h-20 bg-gray-200 dark:bg-gray-700 rounded-full" />
+              )}
+              <span className="text-xs text-gray-500 dark:text-gray-400">
+                Lvl {bp.level}
+              </span>
+            </div>
+          ))}
+      </div>
+    </div>
+  )
+}
+
 interface RouteGroupProps {
   group: RouteWithChildren
   encounterByRoute: Map<number, EncounterDetail>
@@ -1124,22 +1186,7 @@ export function RunEncounters() {
                     </div>
                     {/* Boss pokemon team */}
                     {isBossExpanded && boss.pokemon.length > 0 && (
-                      <div className="flex gap-2 mt-2 flex-wrap">
-                        {boss.pokemon
-                          .sort((a, b) => a.order - b.order)
-                          .map((bp) => (
-                            <div key={bp.id} className="flex items-center gap-1">
-                              {bp.pokemon.spriteUrl ? (
-                                <img src={bp.pokemon.spriteUrl} alt={bp.pokemon.name} className="w-20 h-20" />
-                              ) : (
-                                <div className="w-20 h-20 bg-gray-200 dark:bg-gray-700 rounded-full" />
-                              )}
-                              <span className="text-xs text-gray-500 dark:text-gray-400">
-                                Lvl {bp.level}
-                              </span>
-                            </div>
-                          ))}
-                      </div>
+                      <BossTeamPreview pokemon={boss.pokemon} />
                     )}
                     </div>
                     {sectionAfter && (