feedback5 CB5: in a boss round's prep a watcher sees the boss field — the scouted player's half (mirrored on the right) with the leader standing at its spawn — instead of the normal board without a boss (community report of 2026-10-06, item 55)

Reproduced in the browser (notes i55-repro, an eliminated guest at the boss round): in the Final Assault fight
the watched boss field shows the leader (enemy_9013_acstmk at 10,3), but in the boss round's prep the
eliminated player saw its own empty normal board (camera 'prep', no leader), and a scout of a teammate was the
normal board too, while the players prepare on their half of the boss field with the leader standing there.
Match.prepFieldMeta: in a boss round's prep the scout is built on the boss field (kind 'boss', BOSS_RECT,
units through finalAssault.js bossFieldPlacement: rows − 7, the right half mirrored with RIGHT ↔ LEFT, the player's side;
nextEnemies keeps the leader's spawn tile); game.js frames it with the boss-field prep camera of that side,
which shows the leader (render/app.js leaderShown). With item 56 an eliminated viewer gets it at the round
start without a tap. After the fix the same run: guest field kind 'boss', camera bossPrep, leader shown.

Golden unchanged. Tests: test/match/feedback5-boss-prep-scout.test.js (new, 2). Docs: design/network.md,
design/client.md (§15).

public/js/screens/game.js

@@ -400,7 +400,10 @@ function MatchScreen() {
     const pf = (Array.isArray(pub?.fields) ? pub.fields : []).find((f) => f && f.fieldId === field.fieldId);
     const members = Array.isArray(pf?.players) ? pf.players : Array.isArray(field.players) ? field.players : [];
     const sides = field.sides && typeof field.sides === 'object' ? field.sides : null;
-    const side = sides && sides[myId] ? sides[myId] : members.length > 1 && members.indexOf(myId) === 1 ? 'R' : 'L';
+    // a scouted board of a boss round's prep (Match.prepFieldMeta: the boss-field rows, `side` = the scouted player's
+    // half) is framed by the boss-field prep camera of that half — the leader standing at its spawn (item 55)
+    const side = field.prep && (field.side === 'L' || field.side === 'R') ? field.side
+      : sides && sides[myId] ? sides[myId] : members.length > 1 && members.indexOf(myId) === 1 ? 'R' : 'L';
     // local simulation (client-side combat) feeds a frame per animation frame: no network jitter buffer
     view.raw?.setLocalFeed?.({ on: !!field.local, speed: field.speed });
     setLayer('ALL');