refactor: update cursor request handling and improve parent request management

- Changed `run_id` to `request_id` in `CursorParent` struct for clarity.
- Enhanced the `prepare` function to handle parent requests asynchronously, ensuring proper error handling for active runs.
- Updated database interactions to include `cursor_request_id` for better tracking of requests.
- Added tests to verify the behavior of reused cursor request IDs and their mapping to distinct executions.

server/tests/schema_upgrade.rs

@@ -0,0 +1,43 @@
+use std::borrow::Cow;
+
+use cursor_server::store::Store;
+use sqlx::{migrate::Migrator, sqlite::SqliteConnectOptions, Row};
+
+#[tokio::test]
+async fn version_two_database_upgrades_with_cursor_request_mapping() {
+    let directory = tempfile::tempdir().unwrap();
+    let database = directory.path().join("upgrade.db");
+    let pool = sqlx::SqlitePool::connect_with(
+        SqliteConnectOptions::new()
+            .filename(&database)
+            .create_if_missing(true),
+    )
+    .await
+    .unwrap();
+    let all = sqlx::migrate!("./migrations");
+    let prior = Migrator {
+        migrations: Cow::Owned(
+            all.iter()
+                .filter(|migration| migration.version <= 2)
+                .cloned()
+                .collect(),
+        ),
+        ignore_missing: false,
+        locking: true,
+        no_tx: false,
+    };
+    prior.run(&pool).await.unwrap();
+    drop(pool);
+
+    let store = Store::connect(&format!("sqlite://{}", database.display()))
+        .await
+        .unwrap();
+    let columns = sqlx::query("PRAGMA table_info(runs)")
+        .fetch_all(store.pool())
+        .await
+        .unwrap();
+
+    assert!(columns
+        .iter()
+        .any(|column| column.get::<String, _>("name") == "cursor_request_id"));
+}