feat: show who reacted, and stop curiosities flooding chat

Reactions only ever showed counts, so with several reactors nobody could
tell who had reacted. Naming everyone on its own line does not scale, so
names now appear in three progressively larger places: a hover tooltip per
button (Java only), a one-line closing summary naming the first
resumo-nomes (3) and collapsing the rest to "+N", and /reacoes for the full
breakdown sent privately.

Reactors' names are captured at react time so the summary survives them
logging off.

Two separate causes of chat flooding:
- every join fired its own curiosity, so a wave of joins produced one each.
  Automatic triggers are now rate-limited by intervalo-minimo-segundos
  (120); a typed /curiosidade still bypasses it.
- a curiosity cost two messages. The button row is now appended to the
  headline instead of being broadcast separately.

Also fixes "1 horas" — CuriosityFactory had its own duration formatting
that missed the earlier plural fix; it now uses Msg.duration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ActvLGJApdxEAd2yfKPwqv

src/main/resources/plugin.yml

@@ -33,6 +33,10 @@ commands:
   reagir:
     description: Reage à última mensagem.
     usage: /reagir <chave>
+  reacoes:
+    description: Mostra quem reagiu à última mensagem.
+    usage: /reacoes
+    aliases: [quemreagiu]
   palpite:
     description: Palpita na adivinha aberta.
     usage: /palpite <nome>