basic filewatcher using websocket

src/shims/fs/echo-guard.js

@@ -0,0 +1,31 @@
+// Shared echo suppression for file watcher.
+// fs operations mark paths as "locally modified" so the watcher client
+// can skip events that originated from this client.
+
+const ECHO_SUPPRESS_MS = 1500;
+const recentOps = new Map(); // normalized path -> timestamp
+
+function normalize(p) {
+  return (p || "")
+    .replace(/\\/g, "/")
+    .replace(/^\/+/, "")
+    .replace(/\/+$/, "");
+}
+
+export function markLocalOp(path) {
+  recentOps.set(normalize(path), Date.now());
+}
+
+export function isRecentLocalOp(path) {
+  const norm = normalize(path);
+  const ts = recentOps.get(norm);
+
+  if (!ts) return false;
+
+  if (Date.now() - ts < ECHO_SUPPRESS_MS) {
+    return true;
+  }
+
+  recentOps.delete(norm);
+  return false;
+}