feat: integrate Pi backend and Pi Web

pi-web/lib/allowed-roots.ts

@@ -0,0 +1,24 @@
+// In-memory roots that should be browsable in addition to roots derived from
+// persisted sessions. Stored on globalThis so Next.js hot-reload keeps them.
+declare global {
+  var __piAllowedRootsCache: { roots: Set<string>; expiresAt: number } | undefined;
+  var __piAdditionalAllowedRoots: Set<string> | undefined;
+}
+
+export function normalizeSlashes(filePath: string): string {
+  return filePath.replace(/\\/g, "/");
+}
+
+export function getAdditionalAllowedRoots(): Set<string> {
+  if (!globalThis.__piAdditionalAllowedRoots) {
+    globalThis.__piAdditionalAllowedRoots = new Set();
+  }
+  return globalThis.__piAdditionalAllowedRoots;
+}
+
+export function allowFileRoot(root: string): void {
+  if (!root) return;
+  const normalizedRoot = normalizeSlashes(root);
+  getAdditionalAllowedRoots().add(normalizedRoot);
+  globalThis.__piAllowedRootsCache?.roots.add(normalizedRoot);
+}