fix(build): disable rolldown native tsconfig discovery

Rolldown reads tsconfig.json natively and applies its jsx options, while
Nitro also mirrors them into transform.jsx. This caused redundant
CONFIGURATION_FIELD_CONFLICT warnings (jsx, jsxImportSource).

Set tsconfig: false so Nitro's resolved config is the single source of
truth, consistent with the Rollup builder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: pi0

src/build/rolldown/config.ts

@@ -15,6 +15,10 @@ export const getRolldownConfig = async (nitro: Nitro): Promise<RolldownOptions>
     platform: nitro.options.node ? "node" : "neutral",
     cwd: nitro.options.rootDir,
     input: nitro.options.entry,
+    // Nitro resolves `tsconfig` and passes relevant options (e.g. `transform.jsx`) explicitly.
+    // Disable Rolldown's own tsconfig discovery to avoid `CONFIGURATION_FIELD_CONFLICT` warnings
+    // and keep behavior consistent with the Rollup builder.
+    tsconfig: false,
     external: [...base.env.external, ...builtinModules, ...builtinModules.map((m) => `node:${m}`)],
     plugins: [...((await baseBuildPlugins(nitro, base)) as RolldownPlugin[])],
     resolve: {