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>

packages/db/src/generate.ts

@@ -230,5 +230,12 @@ export function generateQueriesFile(
   if (usedModels.size > 0) {
     imports.push(`import { ${[...usedModels].sort().join(", ")} } from "./schema.ts";`);
   }
-  return `// AUTO-GENERATED by \`wrnexus db generate\` — do not edit.\n${imports.join("\n")}\n\n${blocks.join("\n\n")}\n`;
+  // The dialect is stamped into the header because it changes the emitted SQL:
+  // postgres uses $1 placeholders where sqlite and mysql use ?. Regenerating
+  // under a different profile therefore rewrites this committed file, and
+  // without the stamp the diff looks like unexplained churn.
+  return (
+    `// AUTO-GENERATED by \`wrnexus db generate\` (dialect: ${dialect}) — do not edit.\n` +
+    `${imports.join("\n")}\n\n${blocks.join("\n\n")}\n`
+  );
 }