status: consolidate the pill to one dot + one word; upgrade the panel

- pill: two host dots -> ONE consolidated state (down > slow > up) —
  the at-a-glance question is 'can I watch?', which is one state;
  per-host detail belongs in the tap panel
- panel: dashed slow-threshold line in the CDN sparkline (drawn at the
  server's real threshold, not a client copy) + origin up/down step
  sparkline so 'how long has the origin been down' is visible
- server: origin probe keeps a 20-sample hist like the CDN probe;
  DEGRADED threshold is now ANIWEB_CDN_KBPS (default 40) and is
  returned in /api/cdn so the UI draws the line at the live value
- tests: pill assertions switched to consolidated states; fixtures
  carry origin hist + threshold; assert both sparklines + threshold line
- docs: README + SPEC synced; preview on :8322 restarted (pid 44382)

static/index.html

@@ -18,7 +18,7 @@
   <form onsubmit="const q=document.getElementById('q').value.trim(); if(q) location='?q='+encodeURIComponent(q); return false">
     <input id="q" placeholder="search anime…" aria-label="search anime" autocomplete="off" autocapitalize="off" spellcheck="false">
   </form>
-  <span id="pill" class="pill"><i class="o"></i><i class="c"></i><span></span></span>
+  <span id="pill" class="pill"><i class="d"></i><span></span></span>
   <span id="me" class="muted"></span>
   <div id="menubox" style="display:none">
     <button id="menu" class="tiny" aria-label="menu" aria-haspopup="true">☰</button>