fix: invalidate rusqlite schema cache for attached databases in simulator

The differential simulator's SQLite schema cache workaround
(pragma_user_version query) only invalidated the main database's schema.
When ALTER TABLE DROP COLUMN was executed on an attached database, other
rusqlite connections still saw the old column count, causing false
divergences between limbo and rusqlite.

Fix by also querying {db_name}.sqlite_master for each attached database,
which forces SQLite to re-read the attached database's schema.

Discovered via seed: 12173377563160143215

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: glommer

testing/simulator/runner/execution.rs

@@ -357,14 +357,15 @@ fn execute_interaction_rusqlite(
     stack: &mut Vec<ResultSet>,
 ) -> turso_core::Result<ExecutionContinuation> {
     tracing::info!("");
+    let attached_dbs = env.attached_dbs.clone();
     let SimConnection::SQLiteConnection(conn) = &mut env.connections[interaction.connection_index]
     else {
         unreachable!()
     };
     match &interaction.interaction {
         InteractionType::Query(query) => {
             tracing::debug!("{}", interaction);
-            let raw_result = execute_query_rusqlite(conn, query);
+            let raw_result = execute_query_rusqlite(conn, query, &attached_dbs);
 
             let is_constraint_error = matches!(
                 &raw_result,
@@ -440,10 +441,23 @@ fn execute_interaction_rusqlite(
 fn execute_query_rusqlite(
     connection: &rusqlite::Connection,
     query: &Query,
+    attached_dbs: &[String],
 ) -> rusqlite::Result<Vec<Vec<SimValue>>> {
     // https://sqlite.org/forum/forumpost/9fe5d047f0
-    // Due to a bug in sqlite, we need to execute this query to clear the internal stmt cache so that schema changes become visible always to other connections
+    // Due to a bug in sqlite, we need to execute this query to clear the internal stmt cache so that schema changes become visible always to other connections.
+    // We must do this for the main database AND all attached databases, otherwise
+    // schema changes (e.g. DROP COLUMN) on attached databases won't be visible to
+    // other connections that have the old schema cached.
     connection.query_one("SELECT * FROM pragma_user_version()", (), |_| Ok(()))?;
+    for db_name in attached_dbs {
+        // Force SQLite to re-read the attached database's schema by querying
+        // its sqlite_master table. This ensures schema changes (e.g. DROP COLUMN)
+        // made by other connections are visible.
+        let _ = connection.execute(
+            &format!("SELECT sql FROM {db_name}.sqlite_master LIMIT 1"),
+            (),
+        );
+    }
     match query {
         Query::Select(select) => {
             let mut stmt = connection.prepare(select.to_string().as_str())?;