n8n: build and live-validate the Workflow Error Handler (WF4)

New central "Fleet Ops — Workflow Error Handler" workflow (Error
Trigger -> safe-report Code node -> POST to the new /workflow-error
endpoint), wired as the Error Workflow on both existing workflows with
no recursive loop on itself. Live-validated end-to-end against the
real Fleet Ops server (register + idempotent re-register), and via a
genuine induced failure on the scheduled-scan workflow (broken URL,
confirmed failure, reverted, confirmed healthy).

Fixed two real bugs found during live testing: Code node needed
"Run Once for Each Item" (not "All Items") for $json binding, and
every HTTP body field had a stray trailing space from the n8n
code-editor's bracket auto-close that broke datetime/enum validation.

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

n8n/workflows/check_drift.py

@@ -32,6 +32,7 @@ WORKFLOWS_DIR = Path(__file__).parent
 KNOWN_WORKFLOWS = [
     ("fleet-ops-vehicle-return.json", "mobilityops-return-processing"),
     ("fleet-ops-data-quality-scan.json", "mobilityops-scheduled-quality-scan"),
+    ("fleet-ops-error-handler.json", "Xppn2rAEqUuyiCJF"),
 ]
 
 # Fields that legitimately differ between a committed definition and the live instance