Stop spamming upstream: drop video download from probe, kill re-rolls

- CDN probe no longer downloads 64KB of video (or even a variant
  playlist): one small master-playlist fetch proves reachability.
  State stays OK/DEGRADED, kbps is no longer measured, and the pill/
  panel only show a rate when one exists.
- hianime: 5x getSourcesNew re-roll -> 1 attempt. The enc payload is
  deterministic per data-id (observed identical across calls), so
  re-rolling only hammered the provider.
- anikoto: 2x re-roll -> 1 attempt per server, same reason.

Kept: idle-gated + 30-min degraded backoff from the previous commit,
the single _get retry (protects real user playback from CF blips),
and the origin page check (the 'down' signal). Net upstream traffic is
now what an actual viewer would generate, nothing more.

static/app.js

@@ -957,12 +957,12 @@ function renderPill(d) {
   p.querySelector(".d").className = "d" + (st ? " " + st : "");
   p.querySelector("span").textContent =
     !st ? "…" : st === "down" ? "down"
-    : st === "slow" ? "slow · " + d.kbps + " KB/s" : "up";
+    : st === "slow" ? "slow" + (d.kbps ? " · " + d.kbps + " KB/s" : "") : "up";
   p.title = "upstream site: " + d.origin.state + (d.origin.msg ? " — " + d.origin.msg : "")
-    + "  ·  video CDN: " + d.state + " — " + d.kbps + " KB/s";
+    + "  ·  video CDN: " + d.state + (d.kbps ? " — " + d.kbps + " KB/s" : "");
   p.setAttribute("aria-label", "status: " + (!st ? "checking"
     : st === "down" ? "down — upstream " + d.origin.state
-    : st === "slow" ? "slow — CDN " + d.state + ", " + d.kbps + " KB/s"
+    : st === "slow" ? "slow — CDN " + d.state + (d.kbps ? ", " + d.kbps + " KB/s" : "")
     : "up"));
 }
 
@@ -982,12 +982,12 @@ function renderStatusPanel(d) {
   w.replaceChildren();
   w.append(el("div", "sp-row", "upstream: " + d.origin.state
     + (d.origin.msg ? " (" + d.origin.msg + ")" : "")));
-  w.append(el("div", "sp-row", "CDN: " + d.state + " — " + d.kbps + " KB/s"));
+  w.append(el("div", "sp-row", "CDN: " + d.state + (d.kbps ? " — " + d.kbps + " KB/s" : "")));
   const ch = d.hist || [];
   if (ch.length > 1) {
-    w.append(sparkline(ch.map(s => s.kbps), d.threshold));
-    w.append(el("div", "sp-cap", "CDN, last " + _mins(ch)
-      + " min (dashed = slow threshold " + Math.round(d.threshold) + " KB/s)"));
+    w.append(sparkline(ch.map(s => s.kbps), d.kbps ? d.threshold : null));
+    w.append(el("div", "sp-cap", "CDN, last " + _mins(ch) + " min"
+      + (d.kbps ? " (dashed = slow threshold " + Math.round(d.threshold) + " KB/s)" : "")));
   }
   const oh = d.origin.hist || [];
   if (oh.length > 1) {