feat(260717-v6c): add markCampaignAccidentalReport + generateAndPostAccidentalReportNote

- generateAndPostAccidentalReportNote mirrors generateAndPostAcknowledgment:
  fixed customer-visible template (noteType 18/publish 1), per-ticket
  try/catch isolation, zero evidence interpolation (T-23-01)
- markCampaignAccidentalReport mirrors markCampaignFalsePositive's D-04
  guard/transaction shape, then posts the note post-commit outside the
  FOR UPDATE lock; note-post failure never propagates

lib/services/remediation-service.ts

@@ -28,7 +28,7 @@
 
 import { postgresClient } from './postgres-client';
 import { writeAuditEvent } from './phishing-audit';
-import { generateAndPostAcknowledgment } from './triage-note-service';
+import { generateAndPostAcknowledgment, generateAndPostAccidentalReportNote } from './triage-note-service';
 
 export class RemediationValidationError extends Error {
   constructor(message: string) {
@@ -321,6 +321,91 @@ export async function markCampaignFalsePositive(
   });
 }
 
+// =============================================================================
+// markCampaignAccidentalReport (D-04 guard, quick task 260717-v6c)
+// =============================================================================
+
+export interface MarkAccidentalReportResult {
+  campaignId: string;
+  status: 'accidental_report';
+  auditEventId: string;
+  notePosted: boolean;
+  noteError?: string;
+}
+
+/**
+ * D-04 guard: rejects with RemediationConflictError when any
+ * approved/completed remediation exists for the campaign — mirrors
+ * markCampaignFalsePositive exactly. Otherwise sets
+ * campaigns.status='accidental_report' and writes one atomic audit row
+ * recording the previous status and the optional reason. AFTER the
+ * transaction commits, posts a fixed-template customer-visible note to every
+ * reporting employee's ticket (generateAndPostAccidentalReportNote) — this
+ * external Autotask call runs outside the FOR UPDATE-locked transaction and
+ * its failure is caught/logged, never propagated: the committed status
+ * change is returned regardless, with notePosted/noteError reflecting the
+ * note outcome.
+ */
+export async function markCampaignAccidentalReport(
+  campaignId: string,
+  actor: string | null,
+  reason?: string
+): Promise<MarkAccidentalReportResult> {
+  const result = await postgresClient.transaction(async (client) => {
+    const guardRes = await client.query<{ id: string }>(
+      `SELECT id FROM remediation_actions
+        WHERE campaign_id = $1 AND status IN ('approved', 'completed')
+        FOR UPDATE
+        LIMIT 1`,
+      [campaignId]
+    );
+    if (guardRes.rows.length > 0) {
+      throw new RemediationConflictError(
+        'Cannot mark accidental report: campaign already has approved or completed remediation'
+      );
+    }
+
+    const campaignRes = await client.query<CampaignStatusRow>(
+      `SELECT status FROM campaigns WHERE id = $1`,
+      [campaignId]
+    );
+    const campaign = campaignRes.rows[0];
+    if (!campaign) {
+      throw new RemediationValidationError('Campaign not found');
+    }
+    const previousStatus = campaign.status;
+
+    await client.query(
+      `UPDATE campaigns SET status = 'accidental_report', updated_at = NOW() WHERE id = $1`,
+      [campaignId]
+    );
+
+    const auditEventId = await writeAuditEvent(
+      {
+        campaignId,
+        actor,
+        eventType: 'campaign_marked_accidental_report',
+        payload: { previousStatus, reason: reason ?? null },
+      },
+      client
+    );
+
+    return { campaignId, status: 'accidental_report' as const, auditEventId };
+  });
+
+  let notePosted = false;
+  let noteError: string | undefined;
+  try {
+    await generateAndPostAccidentalReportNote(campaignId);
+    notePosted = true;
+  } catch (err) {
+    console.error('[MARK-ACCIDENTAL-REPORT] accidental-report note post failed', campaignId, err);
+    noteError = err instanceof Error ? err.message : 'Unknown error';
+  }
+
+  return { ...result, notePosted, noteError };
+}
+
 // =============================================================================
 // autoPostAcknowledgment (AUTOGATE-03 gap closure — CR-01 / WR-01)
 // =============================================================================

lib/services/triage-note-service.ts

@@ -251,3 +251,56 @@ export async function generateAndPostAcknowledgment(campaignId: string): Promise
 
   return { noteText, tickets };
 }
+
+/**
+ * Quick task 260717-v6c: posts a short, fixed-template customer-visible note
+ * to every ticket linked to a campaign that a reviewer has marked as an
+ * accidental report — an employee flagged a legitimate email by mistake.
+ * Mirrors `generateAndPostAcknowledgment`'s structure exactly: same reports
+ * lookup query, same per-ticket try/catch INSIDE the loop (D-05 isolation),
+ * same noteType 18 ("Client Portal Note") / publish 1, same
+ * `{ noteText, tickets }` return shape. The body is a FIXED template with
+ * zero evidence/URL/classification interpolation (T-23-01 invariant) —
+ * nothing from the parsed email or classification reasons is ever placed in
+ * this note.
+ */
+export async function generateAndPostAccidentalReportNote(campaignId: string): Promise<TriageNoteResult> {
+  const reportsRes = await postgresClient.query<Pick<ReportRow, 'id' | 'ticket_id'>>(
+    `SELECT id::text, ticket_id::text AS ticket_id
+       FROM reports WHERE campaign_id = $1 ORDER BY created_at ASC`,
+    [campaignId]
+  );
+  const reports = reportsRes.rows;
+
+  const noteText = [
+    'Thanks for flagging this — after review, this turned out to be a legitimate email that was reported by mistake, not a phishing attempt.',
+    '',
+    "No action is needed on your part, and this report has been closed out. If anything ever looks off in the future, please keep reporting it — that's exactly the right move.",
+  ].join('\n\n');
+
+  const client = getAutotaskClient();
+  const tickets: TriageNotePostResult[] = [];
+  for (const report of reports) {
+    // Per-ticket try/catch is INSIDE the loop (not around it) so one
+    // ticket's write failure never aborts the remaining writes (D-05).
+    try {
+      await client.createEntity('TicketNotes', {
+        ticketID: Number(report.ticket_id),
+        title: 'Thank You — Report Reviewed',
+        description: noteText,
+        noteType: 18, // Client Portal Note — customer-visible
+        publish: 1,
+      });
+      tickets.push({ ticketId: report.ticket_id, posted: true });
+    } catch (err) {
+      console.error('[PHISHING-ACCIDENTAL-REPORT] Failed to post note to ticket', report.ticket_id, err);
+      tickets.push({
+        ticketId: report.ticket_id,
+        posted: false,
+        error: err instanceof Error ? err.message : 'Unknown error',
+      });
+    }
+  }
+
+  return { noteText, tickets };
+}