feat: integrate Pi backend and Pi Web

pi-web/lib/session-path.ts

@@ -0,0 +1,11 @@
+import path from "node:path";
+
+export function sessionPathKey(
+  filePath: string,
+  platform: NodeJS.Platform = process.platform,
+): string {
+  const normalized = platform === "win32"
+    ? path.win32.normalize(filePath)
+    : path.posix.normalize(filePath);
+  return platform === "win32" ? normalized.toLowerCase() : normalized;
+}