[BUG]: `drizzle-kit` generate does not respect `snake_case` config

### 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.15-859cf75

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

1.0.0-beta.15-859cf75

### Other packages

_No response_

### Describe the Bug

**What is the undesired behavior?**
`drizzle-kit` generate does not respect `snake_case` config and ends up generating `camelCase` columns.
```ts
// src/db/index.ts
export const db = drizzle(env.DATABASE_URL, { schema, relations, casing: 'snake_case' })
```
```sql
# sec/db/migrations/20260211172725_famous_iron_patriot/migration.sql
CREATE TABLE "deals" (
"id" integer PRIMARY KEY,
"createdAt" timestamp DEFAULT now() NOT NULL,
"deletedAt" timestamp
);
```

**What are the steps to reproduce it?**
Define schema as above with `casing: 'snake_case'` and run `drizzle-kit generate`.

**What is the desired result?**
```sql
# Expected
CREATE TABLE "deals" (
"id" integer PRIMARY KEY,
"created_at" timestamp DEFAULT now() NOT NULL,
"deleted_at" timestamp
);
```