fix(db): stamp the dialect into generated query files

The same generate command emitted ? one run and $1 the next, which looked
like non-determinism. It is not: postgres uses $1 placeholders where
sqlite and mysql use ?, and the driver comes from the active profile, so
building under a different profile rewrites this committed file.

The header now records the dialect it was generated for, making the flip
visible in the diff and explaining check:generated-types failures instead
of leaving them looking like random churn.

Worth deciding separately: a committed artifact whose contents depend on
the active profile will keep drifting. Either generate per dialect, or
stop committing it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

examples/basic-app/app/db/queries.gen.ts

@@ -1,4 +1,4 @@
-// AUTO-GENERATED by `wrnexus db generate` — do not edit.
+// AUTO-GENERATED by `wrnexus db generate` (dialect: sqlite) — do not edit.
 import type { Db, ExecResult } from "@wrnexus/db";
 import { users } from "./schema.ts";