fix: move delete stream.then after dev-server branch to restore thenable

[tsushanth]

Fixes #2145

What

In packages/start/src/server/handler.ts, the line

delete (stream as any).then;

was executing before the USING_SOLID_START_DEV_SERVER early return. This stripped the .then property from the stream before returning it to the dev server, making it non-thenable.

h3 v2's toResponse / prepareResponseBody no longer recognizes the value as awaitable and falls through to new FastResponse(streamObject, …), which stringifies the body to [object Object].

Why delete stream.then exists

The deletion is there so that the TransformStream path (used for Cloudflare Workers) does not try to await the stream object. It only needs to apply immediately before the new TransformStream() block, not for the dev-server path.

Fix

Move delete (stream as any).then to after the USING_SOLID_START_DEV_SERVER guard. The stream stays thenable when returned to the dev server; the deletion still takes effect for the Cloudflare Workers path that follows.

if (mode === "async") return await stream;

if (globalThis.USING_SOLID_START_DEV_SERVER) return stream;

// remove thenable so h3/Cloudflare Workers do not await the stream object;
// must happen after the dev-server branch so the stream remains awaitable
// when returned to solid-start-dev-server above
delete (stream as any).then;

const { writable, readable } = new TransformStream();
stream.pipeTo(writable);
return readable;

Reproduction

Scaffold a SolidStart 2.0.0-alpha.2 project with @solidjs/vite-plugin-nitro-2 per its README (no mode option on createHandler), run vite dev, and curl http://localhost:5173/ returns [object Object]. After this patch the rendered HTML is returned instead.

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