/** * Adds the nullable `provider_instance_id` routing column to * `provider_session_runtime`. * * Slice D of the provider-array refactor splits "driver kind" from * "configured instance". Existing rows have only the driver name in * `provider_name`; new rows additionally carry the user-defined instance * routing key. The column remains nullable so legacy rows can still decode; * the persistence boundary is responsible for materializing a concrete * instance id before any hot routing path sees the binding. * * The column is nullable on purpose — backfilling it during the migration * would require knowing which configured instance "owned" each historical * session, and that mapping is ambiguous when the user later configures * multiple instances of the same driver. Keeping that compatibility at the * persistence boundary keeps the fallback out of active routing code. */import * as SqlClient from "effect/unstable/sql/SqlClient";import * as Effect from "effect/Effect"; export default Effect.gen(function* () {  const sql = yield* SqlClient.SqlClient;   const columns = yield* sql<{ readonly name: string }>`    PRAGMA table_info(provider_session_runtime)  `;  if (!columns.some((column) => column.name === "provider_instance_id")) {    yield* sql`      ALTER TABLE provider_session_runtime      ADD COLUMN provider_instance_id TEXT    `;  }   yield* sql`    CREATE INDEX IF NOT EXISTS idx_provider_session_runtime_instance    ON provider_session_runtime(provider_instance_id)  `;});