feat: redirect vite.plus vanity domain to installer scripts (#30)

## What

The `vite.plus` apex domain now points at this Worker. This adds a
host-based redirect so the short domain works as an installer entry
point:

| Request | Result |
| --- | --- |
| `https://vite.plus` | 302 -> `https://viteplus.dev/install.sh` |
| `https://vite.plus/ps1` | 302 -> `https://viteplus.dev/install.ps1` |

So `curl https://vite.plus | sh` and `irm https://vite.plus/ps1 | iex`
both work.

## How

New middleware `middleware/02.redirect-vite-plus.ts`, mirroring the
existing `01.redirect-to-custom-domain.ts` pattern with an extracted,
unit-tested `buildViteplusRedirect()` helper.

- Only the `vite.plus` apex host is matched. The canonical
`setup.viteplus.dev` host, the legacy `vp-setup.void.app` host, and
`localhost` (dev) fall through untouched, so the download page and
existing legacy redirect keep working.
- `www.vite.plus` is intentionally not matched (only the apex was
requested).
- Any path other than `/ps1` defaults to `install.sh`; a trailing slash
on `/ps1` is tolerated.

## Tests

Adds `tests/redirect-vite-plus.test.ts` (9 cases): both redirect rules,
trailing slash, arbitrary paths, query strings, and the
null/fall-through cases for other hosts and a missing host header. `vp
check` and `vp test` (31 tests) pass.

## Note for deploy

For these redirects to fire, `vite.plus` must be attached as a custom
domain/route on the deployed Worker, not just pointed via DNS. Once
requests reach the Worker with `Host: vite.plus`, the redirect applies.

Author: fengmk2

middleware/02.redirect-vite-plus.ts

@@ -0,0 +1,20 @@
+import { defineMiddleware } from "void";
+
+// The vite.plus vanity domain exists purely as an installer entry point:
+//   curl https://vite.plus     | sh   -> shell installer
+//   irm  https://vite.plus/ps1 | iex  -> PowerShell installer
+const INSTALL_HOST = "vite.plus";
+const INSTALL_SH = "https://viteplus.dev/install.sh";
+const INSTALL_PS1 = "https://viteplus.dev/install.ps1";
+
+export function buildViteplusRedirect(host: string | undefined, requestUrl: string): string | null {
+  if (host !== INSTALL_HOST) return null;
+  const path = new URL(requestUrl).pathname.replace(/\/+$/, "");
+  return path === "/ps1" ? INSTALL_PS1 : INSTALL_SH;
+}
+
+export default defineMiddleware(async (c, next) => {
+  const target = buildViteplusRedirect(c.req.header("host"), c.req.url);
+  if (target) return c.redirect(target, 302);
+  await next();
+});

tests/redirect-vite-plus.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vite-plus/test";
+import { buildViteplusRedirect } from "../middleware/02.redirect-vite-plus";
+
+describe("buildViteplusRedirect", () => {
+  it("redirects the bare domain to the shell installer", () => {
+    expect(buildViteplusRedirect("vite.plus", "https://vite.plus/")).toBe(
+      "https://viteplus.dev/install.sh",
+    );
+  });
+
+  it("redirects /ps1 to the PowerShell installer", () => {
+    expect(buildViteplusRedirect("vite.plus", "https://vite.plus/ps1")).toBe(
+      "https://viteplus.dev/install.ps1",
+    );
+  });
+
+  it("tolerates a trailing slash on /ps1", () => {
+    expect(buildViteplusRedirect("vite.plus", "https://vite.plus/ps1/")).toBe(
+      "https://viteplus.dev/install.ps1",
+    );
+  });
+
+  it("redirects any other path to the shell installer", () => {
+    expect(buildViteplusRedirect("vite.plus", "https://vite.plus/anything")).toBe(
+      "https://viteplus.dev/install.sh",
+    );
+  });
+
+  it("ignores query strings when picking the target", () => {
+    expect(buildViteplusRedirect("vite.plus", "https://vite.plus/?ref=docs")).toBe(
+      "https://viteplus.dev/install.sh",
+    );
+  });
+
+  it("returns null for the canonical download host", () => {
+    expect(buildViteplusRedirect("setup.viteplus.dev", "https://setup.viteplus.dev/")).toBeNull();
+  });
+
+  it("returns null for the legacy host (handled by its own middleware)", () => {
+    expect(buildViteplusRedirect("vp-setup.void.app", "https://vp-setup.void.app/")).toBeNull();
+  });
+
+  it("returns null for localhost during dev", () => {
+    expect(buildViteplusRedirect("localhost:5173", "http://localhost:5173/ps1")).toBeNull();
+  });
+
+  it("returns null when the host header is missing", () => {
+    expect(buildViteplusRedirect(undefined, "https://vite.plus/")).toBeNull();
+  });
+});