fix(keeper): report migration cooldown as skipped

[ZacLou]

Summary

• detect MigrationCooldownNotMet (chore: add community health files and GitHub setup script #20) as an expected cooldown state
• report it as skipped instead of failures so rebalance no longer pages on the waiting window
• update the migration keeper runbook and add a regression test

closes #725

Validation:

• pnpm --filter @meridian/stellar-sdk-helpers test -- src/migration-keeper.test.ts
• pnpm --filter @meridian/stellar-sdk-helpers typecheck
• pnpm --filter @meridian/stellar-sdk-helpers build

[vercel]

@ZacLou is attempting to deploy a commit to the Collins' projects Team on Vercel.

A member of the Team first needs to authorize it.

[collinsezedike]

@ZacLou I am closing this PR. You are not assigned to #725. You never commented on that issue at all, and five other contributors did, asking to be assigned, before you opened this. You did not just skip the assignment step, you skipped ahead of people who followed it correctly.

This is the fourth time: #712, #715, #730, and #731 were all closed for the same reason, and you were told directly after the last round that opening PRs against unclaimed issues had to stop. It has not stopped.

I am not closing this quietly this time. If this happens again, I will stop reviewing your PRs and stop assigning you issues, regardless of code quality. The quality of your work has never been the problem. Repeatedly ignoring the assignment process, after being corrected for it multiple times, is.

If you want to work on something, comment on the issue and wait to be assigned, the same as everyone else.

[ZacLou]

@collinsezedike You're right, and I apologize.

This was a process failure on my side. I allowed an automated assistant to submit PRs without enforcing your assignment rule, and it skipped ahead of contributors who followed the process correctly. That was not acceptable.

I've stopped that workflow and removed write automation from this organization. I will not open another PR here unless I first comment on the issue, am assigned, and keep the change scoped to that issue. Thank you for the clear warning.