Bracket what-if mode: pick winners, watch the tree fill

A wand toggle turns the bracket interactive: tap a side to send that
team through; W/L placeholders resolve down the tree (pure, tested
logic in src/lib/whatif.ts). Real results always override picks; picks
that stop making sense after an upstream change are pruned. Each open
pairing shows the model's advance probability (ratings.json fetched
lazily), and once your final resolves, a summary banner names your
champion with the model's chance of exactly that run. EN/DE included.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/i18n/de.ts

@@ -158,6 +158,11 @@ export const de: Dict = {
     subtitle: "Die K.-o.-Runden — vom Sechzehntelfinale bis zum Finale.",
     thirdPlacePlayoff: "Spiel um Platz 3",
     advanceTooltip: "Modell: Chance jedes Teams aufs Weiterkommen",
+    whatIf: "Was wäre wenn?",
+    whatIfHint: "Tipp auf ein Team, um es durch den Turnierbaum zu schicken. Echte Ergebnisse bleiben fest. Die Prozente sind die Modell-Sicht auf jede Paarung.",
+    reset: "Auswahl zurücksetzen",
+    champion: "Dein Weltmeister: {team}",
+    pathChance: "Modell-Chance für genau diesen Lauf: {pct}",
   },
   teams: {
     title: "Teams",