[BUG]: Drizzle-kit (beta) no longer generates supabase safe migration files

### Report hasn't been filed before.

- [x] I have verified that the bug I'm about to report hasn't been filed before.

### What version of `drizzle-orm` are you using?

1.0.0-beta.2-86f844e

### What version of `drizzle-kit` are you using?

1.0.0-beta.2-86f844e

### Other packages

_No response_

### Describe the Bug

With drizzle-kit and this config

```
export default defineConfig({
schema: "./src/schema",
out: "./supabase/migrations",
dialect: "postgresql",
dbCredentials: {
url: process.env.DATABASE_URL,
},
migrations: {
prefix: "supabase",
},
});
```

previously this would generate migrations that result in migration files that conform to supabase format:
```
migrations/
├── 20251222212715_windy_celestials.sql
└── 20251222213451_pretty_mockingbird.sql
```

however in beta it seems to generate migrations in this format

```
migrations/
├── 20251222212715_windy_celestials/
│ ├── migration.sql
│ └── snapshot.json
└── 20251222213451_pretty_mockingbird/
├── migration.sql
└── snapshot.json
```

which breaks the natural supabase migration flows.