feedback3: merge W3E — two spectator seats per co-op room (GitHub-relayed community request #26; a remake feature): watch like an eliminated player, never act, no private data

docs/META.md

@@ -203,6 +203,12 @@ player) sends no `g.watch` (it would be refused with `BAD_TARGET 'no such field'
 teammate's battle after the own one gets the watched field again (`_resendBattle`, `b.start watch: true`); the fresh
 screen adopts it as the watched field once per battle (`battle/observe.js resumedWatch`: a living player's teammate
 normal battle in COMBAT, first seen while watching nothing), so the observing pill, 返回战场 and the own row work again.
+Spectator seats (a remake feature, community report #26; server/lobby.js): `opts.spectators` / `addSpectator(id)` register
+a spectator — no PlayerState, a stand-in with `alive: false` — that every watch path treats like an eliminated human
+(`_viewers()`: the first field of each battle, the 联防 spec, the first boss field, `g.watch` anything; `addSpectator`
+also resends the state on a join mid-match and each resume); it never gets `m.private` / `m.toast` / `m.unitStats`, is
+never a field's player or authority, its `b.start` spec omits the players' `contentInfo.funds` (`_spectatorSpec`: read by
+no battle effect), it gets the settlement's `m.result`, and `handle()` answers only its `g.watch` (else `SPECTATOR`).
 The rest of this section is the legacy server-run mode
 (`SP_COMBAT=server`):
 `g.watch { fieldId }`: any live field during COMBAT / 联防; while no battle field is up (PREP, drafts, SETTLE)