prodcom-transcript module: ProdCom proxy + live transcript tile

Milestone 3. Server part proxies /prodcom/* (SSE passthrough included) to
the admin-configured ProdCom URL, adding the Bearer key server-side so it
never reaches browsers; reports proxy health for the admin page. Client
ports the prodcom-listener UI into the module contract: history load,
live SSE with in-place updates of in-progress speech, channel colors,
channel visibility toggles + group presets (persisted per tile), hard
channel filter / text size / timestamps as instance settings, auto-scroll
with a jump-to-latest pill. tools/prodcom-mock.js simulates ProdCom
(word-by-word in-progress speech) for testing; verified against it,
including kill-and-restart recovery.

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

modules/prodcom-transcript/server.js

@@ -0,0 +1,93 @@
+'use strict';
+
+/**
+ * ProdCom Transcript — server part.
+ *
+ * One wildcard route that proxies /prodcom/* (including the SSE transcript
+ * stream) to the ProdCom API configured in the admin page, so browsers never
+ * talk to ProdCom directly (no CORS, and the API key never reaches clients).
+ * Ported from prodcom-listener/server.js.
+ */
+
+const http = require('http');
+
+// Hop-by-hop headers that must not be forwarded
+const HOP_HEADERS = new Set([
+  'connection', 'keep-alive', 'proxy-authenticate', 'proxy-authorization',
+  'te', 'trailer', 'transfer-encoding', 'upgrade',
+]);
+
+/** Health shown in the admin page: outcome of the most recent proxied request. */
+let health = { status: 'connecting', message: 'No traffic yet' };
+
+function proxy(req, res, target, apiKey) {
+  const upstreamPath = (req.wildcard || '/') + (req.search || '');
+  const headers = {};
+  for (const [k, v] of Object.entries(req.headers)) {
+    if (!HOP_HEADERS.has(k.toLowerCase())) headers[k] = v;
+  }
+  headers.host = target.host;
+  delete headers['accept-encoding']; // keep SSE unbuffered and simple
+  if (apiKey) headers.authorization = 'Bearer ' + apiKey;
+
+  const preq = http.request(
+    {
+      hostname: target.hostname,
+      port: target.port || 80,
+      path: upstreamPath,
+      method: req.method,
+      headers,
+    },
+    (pres) => {
+      health = { status: 'ok', message: `ProdCom reachable (last: HTTP ${pres.statusCode})` };
+      const outHeaders = {};
+      for (const [k, v] of Object.entries(pres.headers)) {
+        if (!HOP_HEADERS.has(k.toLowerCase())) outHeaders[k] = v;
+      }
+      res.writeHead(pres.statusCode, outHeaders);
+      // Flush immediately — SSE streams may send no bytes for a while, and
+      // the browser needs the headers to consider the stream open.
+      res.flushHeaders();
+      pres.pipe(res);
+      // If ProdCom dies mid-stream, pipe() unpipes on error without ending
+      // the browser's response, leaving SSE clients hanging on a dead
+      // stream. Destroy it so they notice immediately and reconnect.
+      pres.on('close', () => {
+        if (!res.writableEnded) res.destroy();
+      });
+    }
+  );
+
+  preq.on('error', (e) => {
+    health = { status: 'error', message: 'ProdCom unreachable: ' + (e.code || String(e)) };
+    if (!res.headersSent) {
+      res.writeHead(502, { 'Content-Type': 'application/json' });
+    }
+    res.end(JSON.stringify({ error: 'ProdCom unreachable', detail: e.code || String(e) }));
+  });
+
+  // Tear down the upstream connection when the browser disconnects
+  res.on('close', () => preq.destroy());
+  req.pipe(preq);
+}
+
+module.exports = {
+  init({ config }) {
+    health = config.prodcomUrl
+      ? { status: 'connecting', message: 'No traffic yet' }
+      : { status: 'error', message: 'No ProdCom URL configured' };
+    return {
+      stop() { /* nothing persistent to tear down — streams die with their sockets */ },
+      health: () => health,
+    };
+  },
+
+  routes({ config, log }) {
+    // An invalid URL throws here, which surfaces as a mount error in /admin.
+    const target = new URL(config.prodcomUrl || 'http://10.3.11.152:24480');
+    log(`proxying /prodcom/* → ${target.origin}`);
+    return {
+      '* /prodcom/*': (req, res) => proxy(req, res, target, config.apiKey || ''),
+    };
+  },
+};