fix(db): return empty arrays from all()/values() on readonly database

The readonly error handler used a bare `return` for all traced methods,
yielding `undefined` even for all() and values() which callers expect
to return arrays. This would crash on .map()/.length if a write query
ever used these methods (e.g. DELETE ... RETURNING *).

Extract handleReadonlyError() helper that returns [] for all/values
and undefined for run/get. Also reduces complexity in the proxy handler.

Author: betegon

src/lib/telemetry.ts

@@ -630,6 +630,19 @@ export function resetReadonlyWarning(): void {
 /** Methods on SQLite Statement that execute queries and should be traced */
 const TRACED_STATEMENT_METHODS = ["get", "run", "all", "values"] as const;
 
+/**
+ * Handle a readonly database error by warning the user and returning a
+ * type-appropriate no-op value. Returns `undefined` for run/get (void / no-row)
+ * and `[]` for all/values (empty result set).
+ */
+function handleReadonlyError(method: string | symbol): unknown {
+  warnReadonlyDatabaseOnce();
+  if (method === "all" || method === "values") {
+    return [];
+  }
+  return;
+}
+
 /**
  * Wrap a SQLite Statement to automatically trace query execution.
  *
@@ -689,8 +702,7 @@ function createTracedStatement<T>(stmt: T, sql: string): T {
               // Handle readonly database gracefully: warn once, skip the write.
               // The CLI still works — reads succeed, only caching/persistence is lost.
               if (isReadonlyError(error)) {
-                warnReadonlyDatabaseOnce();
-                return;
+                return handleReadonlyError(prop);
               }
 
               // Re-throw if repair didn't help or wasn't applicable

test/lib/telemetry.test.ts

@@ -808,6 +808,23 @@ describe("createTracedDatabase", () => {
       db.close();
     });
 
+    test("all() and values() return empty arrays on readonly write", () => {
+      const db = new Database(dbPath);
+      const tracedDb = createTracedDatabase(db);
+
+      const allResult = tracedDb
+        .query("INSERT INTO test (id, name) VALUES (?, ?)")
+        .all(2, "Bob");
+      const valuesResult = tracedDb
+        .query("INSERT INTO test (id, name) VALUES (?, ?)")
+        .values(3, "Charlie");
+
+      expect(allResult).toEqual([]);
+      expect(valuesResult).toEqual([]);
+
+      db.close();
+    });
+
     test("warning message includes helpful instructions", () => {
       const db = new Database(dbPath);
       const tracedDb = createTracedDatabase(db);