Windows: Dev server fails with "/@fsC:" import path (vite multi-entry plugin)

[Obad94]

Steps to reproduce:

1. Clone repo on Windows (Node 20+, pnpm)
2. pnpm install
3. pnpm run dev
4. Console shows error resolving import /@fsc:/... (missing slash after /@fs)

Error:

Failed to resolve import "/@fsc:/.../src/pizzaz/index.jsx"

Root cause:
Helper toFs in vite.config.mts used "/@fs" (no trailing slash), emitting /@fsc:/... on Windows. path.posix.relative was also not Windows-aware.
i,e:

const toFs = (abs: string) => "/@fs" + abs.replace(/\\/g, "/");

const toServerRoot = (abs: string) =>
  "./" + path.posix.relative(process.cwd(), abs).replace(/\\/g, "/");

Fix:
Use "/@fs/" and platform-aware path.relative with a fallback to /@fs for non-relative cases.
i.e:

const toFs = (abs: string) => "/@fs/" + abs.replace(/\\/g, "/");

const toServerRoot = (abs: string) => {
  const rel = path.relative(process.cwd(), abs).replace(/\\/g, "/");
  // If it's not really relative (different drive or absolute), fall back to fs URL
  if (!rel || rel.startsWith("..") || path.isAbsolute(rel)) return toFs(abs);
  return "./" + rel;
};

Validated:

• Windows 11: dev server loads all endpoints (HMR works)
• Linux (Ubuntu): unchanged

No other files changed.