Stream the page shell first so a loader shows while feeds fetch

Opening the page used to block on refreshStale() before a single byte went
out, so the browser sat on a blank tab for the whole fetch. index.php now
renders templates/shell.php (head, header, filters, skeleton loader) and
flushes it, then refreshes and appends templates/content.php, which removes
the loader as the feed HTML arrives.

- templates/layout.php is split into shell.php + content.php
- refresh chip moved to a right-aligned row above the feed: the toolbar
  paints before the refresh report exists
- header story count shows the cached total, then corrects to the real one
- skeleton styles match the card grid and keep the sources' chroma; a
  noscript style hides the loader for clients without JS
- README: file map and page-load lifecycle updated

index.php

@@ -6,13 +6,11 @@ declare(strict_types=1);
 $app = require __DIR__ . '/src/bootstrap.php';
 
 $config = $app['config'];
+$repository = $app['repository'];
 $service = $app['service'];
 
-$refresh = $service->refreshStale();
-
-$sources = $service->sources();
 $activeSource = $_GET['source'] ?? null;
-if (!is_string($activeSource) || !in_array($activeSource, $sources, true)) {
+if (!is_string($activeSource) || $activeSource === '') {
     $activeSource = null;
 }
 
@@ -21,13 +19,41 @@ $activeRange = $_GET['range'] ?? '';
 if (!is_string($activeRange) || !array_key_exists($activeRange, $ranges)) {
     $activeRange = '';
 }
+
 $since = $activeRange !== '' ? gmdate('c', time() - (int) $ranges[$activeRange]) : null;
+$pageSize = (int) $config['page_size'];
 
-$page = $service->page($activeSource, 1, (int) $config['page_size'], $since);
+// Register the configured feeds before anything renders so the filter tabs are
+// complete on a fresh database; refreshStale() repeats the same sync cheaply.
+$repository->syncFeeds($app['feeds']);
 
-echo App\View::render('layout', [
+$sources = $service->sources();
+if ($activeSource !== null && !in_array($activeSource, $sources, true)) {
+    $activeSource = null;
+}
+
+// Send the shell (header, filters and the feed loader) before refreshing, so
+// the loader is on screen while the feeds are being fetched. Nothing may hold
+// those bytes back.
+ini_set('zlib.output_compression', '0');
+while (ob_get_level() > 0 && ob_end_flush()) {
+    // Drop any active output buffers so the shell reaches the browser now.
+}
+
+echo App\View::render('shell', [
     'config' => $config,
     'sources' => $sources,
+    'activeSource' => $activeSource,
+    'activeRange' => $activeRange,
+    'cachedTotal' => $repository->countItems($activeSource, $since),
+]);
+
+flush();
+
+$refresh = $service->refreshStale();
+$page = $service->page($activeSource, 1, $pageSize, $since);
+
+echo App\View::render('content', [
     'activeSource' => $activeSource,
     'activeRange' => $activeRange,
     'page' => $page,