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

README.md

@@ -19,6 +19,9 @@ No framework, no build step. PHP + SQLite for caching, Bootstrap 5 for the UI.
   selection** from the browser (`manage.php`, password protected): add
   channels by `@handle`, disable or remove feeds — no config editing needed.
 - Paginates with a **"Load more stories"** button (AJAX, 20 per page).
+- Streams the page shell (header, filters and a skeleton loader) to the browser
+  **before** the feeds are fetched, so something paints within milliseconds on
+  every open.
 - Caches everything in **SQLite** so page loads never wait on the network; feeds
   are refreshed on demand when stale (default TTL 30 min).
 
@@ -217,13 +220,16 @@ index.php                                            api/items.php
    FeedService::page(source, page, pageSize, since)   ← read path
           └─ FeedRepository::getItems()/countItems()  SQL over the SQLite cache
                  │
-                 └─ View::render('layout' | 'cards')  server-rendered HTML
+                 └─ View::render('cards')  server-rendered HTML
                     (api/items.php returns that HTML inside a JSON envelope)
 ```
 
-**Request lifecycle (page load):** bootstrap → refresh stale feeds → validate
-`source`/`range` → query one page → render `templates/layout.php` which includes
-`templates/cards.php`.
+**Request lifecycle (page load):** bootstrap → sync configured feeds → render
+`templates/shell.php` (head, header, filters, skeleton loader) and **flush it**
+→ refresh stale feeds → query one page → append the rendered
+`templates/content.php` (which includes `templates/cards.php`) and drop the
+loader. The shell paints while the refresh is still running; the loader never
+outlives the fetch — the content chunk removes it as soon as it arrives.
 
 **Request lifecycle (load more):** `assets/app.js` calls `api/items.php` with the
 next `page` (plus current `source` and `range`), receives
@@ -283,7 +289,8 @@ button when `has_more` is false.
 │   ├── ManageAuth.php        manage.php gate: password, CSRF, flash messages
 │   └── View.php              Escaping + render() + labels/colors/time formatting
 ├── templates/
-│   ├── layout.php            Full page shell, filters, grid, empty state, Load more
+│   ├── shell.php             Streamed first: head, header, filters, feed loader
+│   ├── content.php           Streamed after the refresh: grid, empty state, Load more
 │   ├── manage.php            Feed management page (login, add forms, feed list)
 │   └── cards.php             One feed card partial (used by page + API)
 ├── assets/