docs(guides): add manual migration testing playbook

[aqib-rx]

Comprehensive hands-on guide: all migrate commands, the lock, rollback (migrate:down), production run-on-boot, CI/build integration, dev:reset (dialect auto-detect), and troubleshooting for the issues surfaced during team testing (resolve --skip-verify, same-DB drift, fresh recreates).

Summary

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would change existing behavior)
• Documentation update
• Refactor / chore (no user-facing change)

Related issues

Changeset

This repo uses Changesets. If your PR changes any publishable package under packages/*, you must include a changeset:

pnpm changeset

Then commit the generated .changeset/*.md file.

• I added a changeset (or this PR only touches non-publishable code: docs, tests, internal tooling, apps/*)
• I selected the correct semver bump (patch / minor / major)

The changeset-check CI job will fail if a publishable package is modified without a changeset.

Test plan

• pnpm lint
• pnpm check-types
• pnpm build
• Manually verified the change

Checklist

• I read CONTRIBUTING (if it exists)
• My commits follow the Conventional Commits spec (enforced by commitlint)
• I targeted the main branch
• I updated relevant documentation

Screenshots / recordings

Notes for reviewers

[github-actions]

PR title fails Conventional Commits check

Unknown scope "guides" found in pull request title "docs(guides): add manual migration testing playbook". Scope must match one of: nextly, admin, client, ui, adapter-postgres, adapter-mysql, adapter-sqlite, adapter-drizzle, storage-s3, storage-vercel-blob, storage-uploadthing, plugin-form-builder, create-nextly-app, eslint-config, prettier-config, tsconfig, playground, root, ci, docs, deps, release.

Examples of valid titles:

• feat(admin): add role manager dialog
• fix(adapter-postgres): handle connection pool exhaustion
• chore(deps): bump zod to 4.2.0