Mail: instant first paint from the last saved accounts, folders and list; Outlook folders in one batched call; gzip for app files and large mail responses

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server.js

@@ -4,6 +4,7 @@ const http = require('http');
 const fs = require('fs');
 const atomicWrite = require('./atomic');
 const crypto = require('crypto');
+const zlib = require('zlib');
 const path = require('path');
 const { Readable } = require('stream');
 
@@ -121,10 +122,17 @@ function serveStatic(req, res) {
       headers.etag = `W/"${data.length}-${crypto.createHash('sha1').update(data).digest('hex').slice(0, 16)}"`;
       if (req.headers['if-none-match'] === headers.etag) { res.writeHead(304, { etag: headers.etag, 'cache-control': 'no-cache' }); return res.end(); }
     }
+    // text files are sent gzipped when the browser accepts it (the app's scripts are several hundred KB), and the compressed copy is kept per version
+    if (/^(text\/|application\/(json|manifest))|svg/.test(headers['content-type']) && data.length > 1024 && /\bgzip\b/.test(req.headers['accept-encoding'] || '')) {
+      const key = file + ':' + data.length + ':' + (headers.etag || ''); let z = gzCache.get(key);
+      if (!z) { z = zlib.gzipSync(data, { level: 6 }); if (gzCache.size > 200) gzCache.clear(); gzCache.set(key, z); }
+      headers['content-encoding'] = 'gzip'; headers.vary = 'Accept-Encoding'; data = z;
+    }
     res.writeHead(200, headers);
     res.end(data);
   });
 }
+const gzCache = new Map();
 
 // Changes whenever the app's files change, so an open page can tell that a newer version is available.
 const BUILD = (() => { try { return crypto.createHash('sha1').update(fs.readdirSync(PUBLIC).filter(f => /\.(js|css|html)$/.test(f)).sort().map(f => fs.readFileSync(path.join(PUBLIC, f))).join('')).digest('hex').slice(0, 12); } catch { return String(Date.now()); } })();