feat(lobby): block start until everyone submitted; tracks count stepper

- blindtest/mixed: the host can't start until every connected player has
  submitted their track quota — client disables the button with a hint, and
  game:start rejects with TRACKS_PENDING (authoritative)
- tracks-per-player is now a number stepper (− / + buttons + free typing,
  clamped 1..10) instead of fixed 1/2/3 buttons

Verified e2e: start rejected while a player hasn't submitted, accepted once all did.

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

apps/server/src/handlers.ts

@@ -151,6 +151,25 @@ export function registerRoomHandlers(
       })
       return
     }
+    if (hasBlindtest) {
+      const tpp = room.settings.tracksPerPlayer
+      const pending = [...room.players.values()].some(
+        (p) =>
+          p.connected &&
+          p.name !== "" &&
+          room.blindtestTracks.filter((t) => t.submittedBy === p.id).length < tpp
+      )
+      if (pending) {
+        ack({
+          ok: false,
+          error: {
+            code: "TRACKS_PENDING",
+            message: "Tous les joueurs n'ont pas encore soumis leurs titres.",
+          },
+        })
+        return
+      }
+    }
     ack({ ok: true, data: null })
     // Précharge le contenu (pool quiz depuis la DB), puis lance la boucle.
     // Fire-and-forget : la boucle de jeu broadcast son propre état.

apps/web/src/components/lobby-view.tsx

@@ -3,8 +3,10 @@ import {
   Brain,
   Headphones,
   ListMusic,
+  Minus,
   Music,
   Play,
+  Plus,
   Shuffle,
   Trash2,
   type LucideIcon,
@@ -20,7 +22,7 @@ import { useRoomStore } from "@/store/room"
 import { Avatar } from "@/components/avatar"
 
 const QUESTION_OPTIONS = [3, 5, 10]
-const TRACKS_OPTIONS = [1, 2, 3]
+const MAX_TRACKS = 10
 const GAME_TYPES: { value: GameType; label: string; Icon: LucideIcon }[] = [
   { value: "mixed", label: "Mixte", Icon: Shuffle },
   { value: "quiz", label: "Quiz", Icon: Brain },
@@ -35,6 +37,53 @@ const MODE_LABELS: Record<BlindtestMode, string> = {
 const inputClass =
   "border-input bg-background h-10 w-full rounded-md border px-3 py-2 text-sm focus-visible:ring-ring focus-visible:ring-2 focus-visible:outline-none disabled:opacity-50"
 
+function Stepper({
+  value,
+  min = 1,
+  max = MAX_TRACKS,
+  onChange,
+}: {
+  value: number
+  min?: number
+  max?: number
+  onChange: (v: number) => void
+}) {
+  const clamp = (v: number) => Math.max(min, Math.min(max, v))
+  return (
+    <div className="flex items-center gap-1">
+      <Button
+        size="icon-sm"
+        variant="secondary"
+        disabled={value <= min}
+        onClick={() => onChange(clamp(value - 1))}
+      >
+        <Minus />
+      </Button>
+      <input
+        type="number"
+        min={min}
+        max={max}
+        value={value}
+        onChange={(e) => {
+          const n = parseInt(e.target.value, 10)
+          if (!Number.isNaN(n)) {
+            onChange(clamp(n))
+          }
+        }}
+        className="border-input bg-background h-8 w-14 rounded-md border text-center text-sm [appearance:textfield] focus-visible:outline-none [&::-webkit-inner-spin-button]:appearance-none"
+      />
+      <Button
+        size="icon-sm"
+        variant="secondary"
+        disabled={value >= max}
+        onClick={() => onChange(clamp(value + 1))}
+      >
+        <Plus />
+      </Button>
+    </div>
+  )
+}
+
 function shuffle<T>(items: T[]): T[] {
   const arr = [...items]
   for (let i = arr.length - 1; i > 0; i--) {
@@ -90,7 +139,12 @@ export function LobbyView({ snapshot }: { snapshot: RoomSnapshot }) {
     effectiveType === "blindtest" || effectiveType === "mixed"
 
   const rounds = buildRounds(effectiveType, showQuiz ? count : 0, totalTracks)
-  const canStart = rounds.length > 0
+  // Blindtest : tout le monde doit avoir soumis son quota de titres.
+  const allSubmitted =
+    !showBlindtest ||
+    (snapshot.submissions.length > 0 &&
+      snapshot.submissions.every((s) => s.count >= tracksPerPlayer))
+  const canStart = rounds.length > 0 && allSubmitted
 
   async function start() {
     setError(null)
@@ -205,18 +259,10 @@ export function LobbyView({ snapshot }: { snapshot: RoomSnapshot }) {
             <span className="flex items-center gap-1.5 text-sm font-medium">
               <ListMusic className="size-4" /> Titres par joueur
             </span>
-            <div className="flex gap-1">
+            <Stepper
-              {TRACKS_OPTIONS.map((n) => (
+              value={tracksPerPlayer}
-                <Button
+              onChange={(v) => updateSettings({ tracksPerPlayer: v })}
-                  key={n}
+            />
-                  size="sm"
-                  variant={tracksPerPlayer === n ? "default" : "secondary"}
-                  onClick={() => updateSettings({ tracksPerPlayer: n })}
-                >
-                  {n}
-                </Button>
-              ))}
-            </div>
           </div>
         </div>
       )}
@@ -226,9 +272,17 @@ export function LobbyView({ snapshot }: { snapshot: RoomSnapshot }) {
       )}
 
       {isHost ? (
-        <Button disabled={busy || !canStart} onClick={start}>
+        <div className="flex flex-col gap-1">
-          <Play /> {busy ? "Lancement…" : `Lancer (${rounds.length} manches)`}
+          <Button disabled={busy || !canStart} onClick={start}>
-        </Button>
+            <Play /> {busy ? "Lancement…" : `Lancer (${rounds.length} manches)`}
+          </Button>
+          {showBlindtest && !allSubmitted && (
+            <p className="text-muted-foreground text-center text-xs">
+              En attente que tout le monde ait soumis ses {tracksPerPlayer}{" "}
+              titre(s).
+            </p>
+          )}
+        </div>
       ) : (
         <p className="text-muted-foreground text-center text-xs">
           En attente du lancement par l'hôte…