chore: upgrade Rolldown 1.0.0-rc.18, Vitest 5.0.0-beta.1 (#414)

Automated daily upgrade of Vite, Rolldown, and/or Vitest to the latest
available versions.

**Rolldown:** `1.0.0-rc.17` → `1.0.0-rc.18`
**Vitest:** `4.1.5` → `5.0.0-beta.1`

### Updated locations
- `packages/react-server/package.json` — `vite`, `rolldown`
- `test/package.json` — `vite`, `rolldown`, `vitest`, `@vitest/ui`
- `packages/rsc/package.json` — `vitest`, `@vitest/*`
- `packages/create-react-server/test/package.json` — `vitest`
- `package.json` — all `pnpm.overrides` for Vite
- `pnpm-lock.yaml`

### Smoke test
- Dev mode — `hello world` test passed ✅
- Build+start mode — `hello world` test passed ✅

Co-authored-by: lazarv <1749493+lazarv@users.noreply.github.com>

Author: react-server-bot[bot]

packages/create-react-server/test/package.json

@@ -13,6 +13,6 @@
     "clean": "rm -rf .build"
   },
   "devDependencies": {
-    "vitest": "4.1.5"
+    "vitest": "5.0.0-beta.1"
   }
 }

packages/react-server/package.json

@@ -238,7 +238,7 @@
     "react-refresh": "^0.14.2",
     "remark-frontmatter": "^5.0.0",
     "remark-mdx-frontmatter": "^4.0.0",
-    "rolldown": "1.0.0-rc.17",
+    "rolldown": "1.0.0-rc.18",
     "sass": "^1.86.0",
     "semver": "^7.6.3",
     "smol-toml": "^1.6.0",

packages/rsc/package.json

@@ -44,12 +44,12 @@
     "bench:report": "node __bench__/report.mjs --current bench-raw.json --markdown comment.md"
   },
   "devDependencies": {
-    "@vitest/coverage-istanbul": "^4.1.5",
-    "@vitest/coverage-v8": "^4.1.5",
+    "@vitest/coverage-istanbul": "^5.0.0-beta.1",
+    "@vitest/coverage-v8": "^5.0.0-beta.1",
     "react": "0.0.0-experimental-ab18f33d-20260220",
     "react-dom": "0.0.0-experimental-ab18f33d-20260220",
     "react-server-dom-webpack": "0.0.0-experimental-ab18f33d-20260220",
-    "vitest": "^4.1.5"
+    "vitest": "^5.0.0-beta.1"
   },
   "peerDependencies": {
     "react": ">=19.0.0 || >=0.0.0-experimental"