从 Mailgun 迁移

I am moving an email integration from Mailgun to Bird. Route through it with me.
1. Check what you already have before setting anything up. If Bird's MCP server is connected, use its tools. If the Bird CLI is installed and signed in, use that. Either one is enough, and every step below is an action you take with whichever you have. Only if neither is present, follow https://bird.com/docs/ai/set-up-your-agent.md to set one up and sign me in. Every Bird docs page serves Markdown at its own URL with `.md` appended, so fetch that rather than the HTML.
2. Read https://bird.com/docs/guides/email/migrate/mailgun.md for the parameter, suppression and event mapping, and https://bird.com/docs/guides/email/migrate.md for the order the steps go in.
3. Find and list my Mailgun usage in this repository before you change anything: the /v3/{domain}/messages call sites and any SDK wrappers around them, every o:, v: and h: prefixed parameter I pass, my webhook handler and the URL it is registered at, and every Mailgun domain I send from. Mailgun scopes almost everything per domain, so keep that list of domains: the next two steps both work through it.
4. Register each of those sending domains with Bird and give me the DNS records to publish, following https://bird.com/docs/guides/email/sending-domains.md. Leave every DNS record Mailgun uses exactly as it is: Bird's records are published alongside them and both providers authenticate side by side until I switch traffic. Publishing DNS affects mail for the whole domain, so show me the records and let me publish them.
5. Export my suppressions from Mailgun and import them into Bird before any production traffic goes through Bird, so my first sends do not reach addresses that already bounced or complained. Mailgun keeps three lists per domain, so pull GET /v3/{domain}/bounces, GET /v3/{domain}/complaints and GET /v3/{domain}/unsubscribes for every domain you found. The Bird import takes one address per request and is idempotent, so a partial re-run is safe. https://bird.com/docs/guides/email/suppressions.md has the reason taxonomy.
6. Port the send call and the webhook handler using the mapping tables on the provider page. Two things need attention rather than translation: Mailgun reports one failed event with a severity field where Bird has separate deferred and bounced events, and Bird signs deliveries per Standard Webhooks rather than Mailgun's scheme, so treat verification as a rewrite. See https://bird.com/docs/guides/webhooks.md and https://bird.com/docs/guides/email/events.md.
7. Run my whole integration against Bird's mail sandbox before any production traffic, following https://bird.com/docs/guides/email/testing-sandbox.md. Sandbox sends run the real pipeline without reaching an inbox or touching my sending reputation.
8. Stop and ask me wherever a step needs a decision. Do not point production traffic at Bird until I have seen the sandbox results and replied with the words cut over to Bird. Retiring the Mailgun path is a separate step that comes later: ask me again and wait for me to reply with the words retire the Mailgun path. A reply that agrees without naming what it is authorising is not authorisation. Finish by telling me what is left that only a person can do.