[BUG]: drizzle-seed throws on tables with two composite unique constraints sharing a column

### 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.22

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

1.0.0-beta.22

### Other packages

drizzle-seed@1.0.0-beta.22

### Describe the Bug

`seed()` throws when a table declares **two composite unique constraints that share a column**. This is a common multi-tenant pattern: a `(tenant_id, id)` composite unique to serve as a composite-FK target, plus a `(tenant_id, business_key)` unique for the per-tenant business rule. `PostgreSQL` supports this without issue, but `drizzle-seed` rejects it.

**Error**

```
Error: Currently, multiple composite unique keys that share the same column are not supported.
at SeedService.generatePossibleGenerators (drizzle-seed/src/SeedService.ts:359)
at seedPostgres (drizzle-seed/src/pg-core/index.ts:63)
at seedFunc (drizzle-seed/src/index.ts:347)
...
```

**Minimal reproduction**

```ts
import { pgTable, uuid, text, unique } from "drizzle-orm/pg-core";
import { drizzle } from "drizzle-orm/postgres-js";
import { seed } from "drizzle-seed";
import postgres from "postgres";

const products = pgTable(
"products",
{
id: uuid("id").primaryKey().defaultRandom(),
orgId: uuid("org_id").notNull(),
name: text("name").notNull(),
},
(t) => [
// composite-FK target so children can enforce same-tenant references
unique("products_org_id_unique").on(t.orgId, t.id),
// per-tenant business uniqueness
unique("products_org_name_unique").on(t.orgId, t.name),
],
);

const db = drizzle(postgres(process.env.DATABASE_URL!));
await seed(db, { products }); // throws
```

**Expected behavior**

`drizzle-seed` should generate rows that satisfy both composite unique constraints (both constraints are independently valid in PostgreSQL), rather than throwing.

**Actual behavior**

`generatePossibleGenerators` throws unconditionally as soon as two composite unique constraints share a column. Providing explicit generators via `.refine()` for the columns involved does not help — the check is structural and runs before generators are applied.

Start in drizzle-seed/src/SeedService.ts at generatePossibleGenerators, then trace the calls through drizzle-seed/src/pg-core/index.ts and drizzle-seed/src/index.ts. Reproduce the schema from the issue and determine how generation handles two composite unique constraints sharing a column; done means seed() completes and generated rows satisfy both constraints without the structural rejection.

Written by the indexing model from the issue text.