Add web/ — PTY+WebSocket server, xterm.js PWA client, Dockerfile, and PyInstaller notes

web/static/sw.js

@@ -0,0 +1,22 @@
+const CACHE = "kanjin-v1";
+const PRECACHE = ["/", "/static/manifest.json"];
+
+self.addEventListener("install", (e) => {
+    e.waitUntil(
+        caches.open(CACHE).then((c) => c.addAll(PRECACHE)).then(() => self.skipWaiting())
+    );
+});
+
+self.addEventListener("activate", (e) => {
+    e.waitUntil(
+        caches.keys().then((keys) =>
+            Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k)))
+        ).then(() => self.clients.claim())
+    );
+});
+
+self.addEventListener("fetch", (e) => {
+    e.respondWith(
+        caches.match(e.request).then((r) => r || fetch(e.request))
+    );
+});