You are helping me build the following AI agent workflow.

## Goal
Lead-to-Client Pipeline with CRM: Monitors your Google Sheet for lead status changes to send booking or proposal emails, append new clients, and calculate delivery duration.

## Specification
- What it does: You get automatic booking or proposal emails sent via Gmail the moment your Google Sheet shows a lead is qualified or awaiting a proposal. New clients are instantly added to your tracking sheet when deals close, and delivery duration metrics update automatically once projects are marked as delivered.
- Trigger: Triggered by an event (Event · on Google Sheets edit)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - Google Sheets: CRM data storage and trigger source
  - n8n: Workflow orchestration and branching logic
  - Gmail: Sending automated emails for lead stages
  - Code: Processing timestamps and calculating delivery duration

## Known pitfalls, handle each one explicitly in your implementation
1. Timestamp format mismatches often break calculations, so ensure all date strings are parsed using a consistent library like dayjs before computing differences.
2. Webhook security is critical for n8n endpoints, so enforce authentication headers or IP whitelisting to prevent unauthorized trigger requests.

## Reference implementation
https://n8n.io/workflows/7514 (workflow template)
Fetch and inspect this before building. If it matches my stack, adapt it;
if not, rebuild the pattern with my tools.

## Process requirements
1. Before building: ask me which of the listed tools I actually use and
   what my platform is (n8n / Make / code / other). Do not assume.
2. Adapt the pattern to my answers; do not force the reference stack.
3. Address every pitfall above; tell me how you handled each.
4. Provide a test plan I can run before letting this touch real data.
5. Ask before any step that sends messages, modifies data, or spends money.

Source: https://usecasesforagents.com/use-case/automated-lead-to-client-pipeline-with-crm/ via usecasesforagents.com