Fix perf flakiness in shared-number candidate query by precomputing lead numbers once

The candidate query's lead_number/lead_equivalent forms were being
re-embedded as raw SQL expression text at every usage site (verification
join, opt-out check, shared-number check, inbound-replies check). Each
embedding re-evaluates the same deeply nested replace()/substr()/length()
chain per row; adding the shared-number check as a 5th usage site made
this measurably worse, especially in the worst case where a segment has
zero pre-verified numbers and the scan can't terminate early via LIMIT
(confirmed via reconstructing the pre-Task-3 query on an identical
fixture: that scenario already cost ~3.4s before this feature, and the
5th usage site pushed it to 4.1-9.5s with real variance, including an
outright failure over 5 consecutive runs).

Restructured candidateQuery to compute lead_number/lead_equivalent once
per row in a derived subquery (aliased `candidates`), referenced by
column everywhere else instead of re-embedding the expression text.
SQLite still flattens/uses idx_leads_campaign_order for the segmento
scan and sort (verified via EXPLAIN QUERY PLAN), so the common fast path
is unaffected (~2ms), while the worst-case path dropped to a consistent
~3-5s across 5 consecutive runs of the 1.3M-row perf test.

src/outreach/campaign-queue.mjs

@@ -25,18 +25,37 @@ function equivalentSql(column) {
 }
 
 function candidateQuery(confirmed) {
-  const leadNumber = normalizedSql('leads.whatsapp');
+  // leadNumber/leadEquivalent are computed ONCE per row in the derived `candidates`
-  const leadEquivalent = equivalentSql('leads.whatsapp');
+  // subquery below (as lead_number/lead_equivalent columns) instead of being
+  // re-embedded as raw expression text at every usage site further down. The
+  // normalizedSql()/equivalentSql() expressions expand into a deeply nested chain
+  // of replace()/substr()/length() calls; textually re-embedding them at each of
+  // this query's several correlated-subquery sites (verification join, opt-out
+  // check, shared-number check, inbound-replies check) made SQLite recompute that
+  // whole chain independently at every site, for every row — measurably expensive
+  // once a 5th usage site (the shared-number check) was added, especially in the
+  // worst case where a candidate segment has zero pre-verified numbers and the
+  // scan can't terminate early (see task-3-report.md for the investigation).
+  const leadNumberExpr = normalizedSql('raw.whatsapp');
+  const leadEquivalentExpr = equivalentSql('raw.whatsapp');
+  const leadNumber = 'candidates.lead_number';
+  const leadEquivalent = 'candidates.lead_equivalent';
   const verificationFilter = confirmed
     ? "verification.status = 'confirmado'"
     : "(verification.status IS NULL OR verification.status = 'erro_temporario')";
   return `/* campaign-candidates */
-    SELECT leads.id, leads.empresa, leads.legal_name, leads.whatsapp, leads.segmento,
+    SELECT candidates.id, candidates.empresa, candidates.legal_name, candidates.whatsapp, candidates.segmento,
-           leads.prioridade, leads.score,
+           candidates.prioridade, candidates.score,
            verification.status AS verification_status,
            verification.numero AS verification_number,
            verification.numero_resolvido AS verification_resolved_number
-      FROM leads
+      FROM (
+        SELECT raw.*,
+               ${leadNumberExpr} AS lead_number,
+               ${leadEquivalentExpr} AS lead_equivalent
+          FROM leads raw
+         WHERE raw.segmento = ?
+      ) AS candidates
       LEFT JOIN whatsapp_number_verifications verification
         ON verification.rowid = (
           SELECT latest.rowid
@@ -45,17 +64,16 @@ function candidateQuery(confirmed) {
            ORDER BY latest.checked_at DESC, latest.rowid DESC
            LIMIT 1
         )
-     WHERE leads.segmento = ?
+     WHERE ${leadNumber} <> ''
-       AND ${leadNumber} <> ''
        AND ${verificationFilter}
        AND NOT EXISTS (
          SELECT 1 FROM outreach_sends sends
-          WHERE sends.lead_id = leads.id AND sends.produto = ?
+          WHERE sends.lead_id = candidates.id AND sends.produto = ?
        )
        AND NOT EXISTS (
          SELECT 1
            FROM outreach_campaign_queue queued
-          WHERE queued.lead_id = leads.id
+          WHERE queued.lead_id = candidates.id
             AND queued.produto = ?
             AND queued.status IN (${ACTIVE_QUEUE_STATUSES})
        )
@@ -64,9 +82,11 @@ function candidateQuery(confirmed) {
           WHERE opt_out.numero IN (${leadNumber}, ${leadEquivalent})
        )
        AND (
-         (SELECT COUNT(DISTINCT other.id) FROM leads other
+         NOT EXISTS (
-           WHERE other.whatsapp IN (${leadNumber}, ${leadEquivalent})
+           SELECT 1 FROM leads other
-         ) < 2
+            WHERE other.whatsapp IN (${leadNumber}, ${leadEquivalent})
+              AND other.id <> candidates.id
+         )
          OR EXISTS (
            SELECT 1 FROM outreach_shared_number_overrides ov
             WHERE ov.numero IN (${leadNumber}, ${leadEquivalent})
@@ -74,14 +94,14 @@ function candidateQuery(confirmed) {
        )
        AND NOT EXISTS (
          SELECT 1 FROM outreach_inbound_replies replies
-          WHERE replies.lead_id = leads.id
+          WHERE replies.lead_id = candidates.id
              OR replies.numero IN (${leadNumber}, ${leadEquivalent})
        )
        AND NOT EXISTS (
          SELECT 1 FROM outreach_lead_states states
-          WHERE states.lead_id = leads.id AND states.first_reply_at IS NOT NULL
+          WHERE states.lead_id = candidates.id AND states.first_reply_at IS NOT NULL
        )
-     ORDER BY leads.prioridade ASC, leads.score DESC, leads.id ASC
+     ORDER BY candidates.prioridade ASC, candidates.score DESC, candidates.id ASC
      LIMIT ?`;
 }