feat: redirect vp-setup.void.app to setup.viteplus.dev (#4)

## Summary

- Added global Void middleware at
`middleware/01.redirect-to-custom-domain.ts` that issues a 301 redirect
from the default `vp-setup.void.app` host to the canonical custom domain
`https://setup.viteplus.dev`, preserving path and query string
- Other hosts (custom domain itself, `localhost` during dev, any
preview/staging subdomains) pass through untouched
- Exported a pure `buildRedirectTarget()` helper so the logic is
unit-testable without spinning up Hono

## Test plan

- [x] `vp test` — 30 tests pass (6 new in `tests/redirect.test.ts`)
- [x] `vp check` — clean (format, lint, type-check)
- [ ] After merge + deploy:
- [ ] `curl -I https://vp-setup.void.app/` returns `301` with `Location:
https://setup.viteplus.dev/`
- [ ] `curl -IL 'https://vp-setup.void.app/?tag=v1.2.3&arch=arm64'`
preserves query and lands on 200
- [ ] `curl -I https://setup.viteplus.dev/` returns `200` (no redirect
loop)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: fengmk2

middleware/01.redirect-to-custom-domain.ts

@@ -0,0 +1,16 @@
+import { defineMiddleware } from "void";
+
+const LEGACY_HOST = "vp-setup.void.app";
+const CANONICAL_ORIGIN = "https://setup.viteplus.dev";
+
+export function buildRedirectTarget(host: string | undefined, requestUrl: string): string | null {
+  if (host !== LEGACY_HOST) return null;
+  const url = new URL(requestUrl);
+  return `${CANONICAL_ORIGIN}${url.pathname}${url.search}`;
+}
+
+export default defineMiddleware(async (c, next) => {
+  const target = buildRedirectTarget(c.req.header("host"), c.req.url);
+  if (target) return c.redirect(target, 301);
+  await next();
+});

tests/redirect.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vite-plus/test";
+import { buildRedirectTarget } from "../middleware/01.redirect-to-custom-domain";
+
+describe("buildRedirectTarget", () => {
+  it("redirects legacy host root to canonical origin", () => {
+    expect(buildRedirectTarget("vp-setup.void.app", "https://vp-setup.void.app/")).toBe(
+      "https://setup.viteplus.dev/",
+    );
+  });
+
+  it("preserves path and query string", () => {
+    expect(
+      buildRedirectTarget("vp-setup.void.app", "https://vp-setup.void.app/?tag=v1.2.3&arch=arm64"),
+    ).toBe("https://setup.viteplus.dev/?tag=v1.2.3&arch=arm64");
+  });
+
+  it("returns null for the custom domain (no redirect)", () => {
+    expect(buildRedirectTarget("setup.viteplus.dev", "https://setup.viteplus.dev/")).toBeNull();
+  });
+
+  it("returns null for localhost during dev", () => {
+    expect(buildRedirectTarget("localhost:5173", "http://localhost:5173/")).toBeNull();
+  });
+
+  it("returns null when host header is missing", () => {
+    expect(buildRedirectTarget(undefined, "https://vp-setup.void.app/")).toBeNull();
+  });
+
+  it("does not match preview/staging subdomains", () => {
+    expect(
+      buildRedirectTarget("vp-setup-staging.void.app", "https://vp-setup-staging.void.app/"),
+    ).toBeNull();
+  });
+});