Docs, README, launchers, PWA install

Milestone 7. docs/MODULE-GUIDE.md documents the whole module contract
from an author's point of view — manifest reference, client factory +
moduleApi, server init/routes/health, scoping and resilience rules, a
copy-paste minimal module, and a testing section with the two mocks and a
resilience checklist. README rewritten with run/configure/use
instructions in the prodcom-listener style, plus double-click launchers
for macOS and Windows. PWA: manifest, icons, and a minimal network-first
service worker that never touches /api/*.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RNYUv9EyrGSFmCnmH7WYKH

public/sw.js

@@ -0,0 +1,45 @@
+'use strict';
+
+/* Minimal service worker: caches the shell so the PWA is installable.
+   Never touches /api/* (live data + SSE streams). Network-first, so open
+   dashboards always run the latest shell when the server is reachable. */
+
+const CACHE = 'proddash-v1';
+const SHELL = [
+  '/',
+  '/style.css',
+  '/shell.js',
+  '/manifest.webmanifest',
+  '/icons/icon-192.png',
+  '/icons/icon-512.png',
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE).then((cache) => cache.addAll(SHELL)).then(() => self.skipWaiting())
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys()
+      .then((keys) => Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k))))
+      .then(() => self.clients.claim())
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  const url = new URL(event.request.url);
+  if (event.request.method !== 'GET' || url.pathname.startsWith('/api/')) return;
+
+  // Network first, cache fallback
+  event.respondWith(
+    fetch(event.request)
+      .then((res) => {
+        const copy = res.clone();
+        caches.open(CACHE).then((cache) => cache.put(event.request, copy));
+        return res;
+      })
+      .catch(() => caches.match(event.request, { ignoreSearch: true }))
+  );
+});