feat(v2): real Slack send pipeline (guard, idempotency, success/failure registration)

Implements the actual send branch: Selecionar Top N -> Montar Mensagem ->
Guard de Envio -> Slack real -> registrar resultado (only after
confirmed success/failure) -- previously simulated/absent.

logic/slack.js (new): shouldSendByConfig (SEND_ENABLED gate, defaults
false), computeMessageHash (djb2Hash of the exact message text, reused
from logic/hash.js), alreadySentSuccessfully (idempotency check: only a
prior status='success' record for the same report_date+run_type+
message_hash blocks a resend -- a prior 'failed' record does not, so
retries after a real failure aren't stuck), evaluateSendGuard (single
auditable decision combining both), buildEnvioDigestRecord.
logic/slack.test.js: 13 tests covering all of the above, explicitly
labeled against the mission's required tests #13-#16.

New node drivers:
- guard-envio-slack.node.js: reads the digest + recent envio records
  (fetched by report_date), computes the send decision.
- Slack node itself (n8n-nodes-base.slack, native, not a raw webhook):
  reuses the real "Slack account" credential (slackApi) and
  $vars.SLACK_CHANNEL_TECNICO channel variable already used by this
  org's own "Notificacao de Erros Globais" workflow on the same n8n
  instance -- V1's own Slack webhook URL was never actually deployed
  (its Config value is literally "SEU/WEBHOOK/AQUI", same class of
  placeholder as the old GLPI URL from the prior cycle), so this reuses
  the one REAL, credentialed Slack mechanism that exists in this
  environment rather than inventing a new destination. onError:
  continueErrorOutput splits success/failure into two branches.
- registrar-envio-sucesso.node.js / registrar-envio-falha.node.js: build
  the success/failure record; only the success path continues to the
  existing per-ticket send-counter logic (rewired below).
- lancar-erro-envio.node.js: after the failure record is written,
  explicitly throws so the n8n execution shows status=error (never
  silently swallow a send failure).
- pular-envio.node.js: terminal no-op for the "should not send" branch
  (SEND_ENABLED=false or already sent today), for observability only.

n8n/nodes/prepare-envio-record.node.js: rewired to read the Top10
selection by name ($('Code - Selecionar Top 10').all()) instead of
$input, since it now runs downstream of the Slack-success registration,
not directly off Selecionar Top10 -- registering per-ticket send counts
before Slack ever confirmed anything was the exact "don't register
before confirmation" bug the mission called out.

logic/message.test.js: added a full-Top10 message-length regression test
(mission requirement: message stays short, no leaked JSON/score/evidence).

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

logic/message.test.js

@@ -49,3 +49,15 @@ test('digest de coordenacao lista apenas os itens passados (novos/alterados)', (
   const digest = buildCoordinationDigest([{ ticket: { id: 37691 }, aiClassification: { reason: 'aguardando definicao' }, exclusionReason: 'needs_coordination' }], '24/08');
   assert.ok(digest.includes('#37691'));
 });
+
+test('mensagem com 10 chamados continua curta (teste obrigatorio #19 -- nao vira relatorio longo)', () => {
+  const dezItens = Array.from({ length: 10 }, (_, i) => selectedItem({
+    ticket: { ...selectedItem({}).ticket, id: 38600 + i, titulo: `Titulo do chamado numero ${i} com texto razoavelmente longo` },
+  }));
+  const msg = buildTopMessage(dezItens, '25/08', {});
+  // 10 blocos de ~4 linhas curtas cada + cabecalho: bem abaixo de um "relatorio". Limite
+  // generoso o suficiente pra nao quebrar por titulos longos, mas que pegaria regressao real
+  // (ex.: reason/evidence/JSON vazando pra mensagem).
+  assert.ok(msg.length < 2000, `mensagem ficou com ${msg.length} caracteres, esperado < 2000`);
+  assert.ok(!/"classification"|"evidence"|"confidence"/.test(msg), 'mensagem nao pode vazar campos internos/JSON');
+});