fix(plex): the slow line says both rates in one unit

Each rate took its own unit, so a link under a megabit read "needs 1.4
Mbps, 800 kbps arrives". `fmtBitrates` picks the unit the largest takes
for all of them. The away-window header now says what ends an absence
outside hls.js (the answer) and after the error (the viewer's retry).

frontend/src/lib/hlsEngine.ts

@@ -31,10 +31,12 @@ export const RECLAIM_WINDOW_MS = 120_000;
 // less often, and says it cannot play only once the server has been away this long. It used to say
 // so at the first 502, over a picture still playing from the buffer, and never asked again.
 //
-// The absence ends when MEDIA arrives again (a fragment loads), not when a session request is
-// answered: a server that answers every session and delivers none of them is still not serving, and
-// ending the absence at each answer restarted the stream forever. The same window bounds a link too
-// slow for the stream (see `slowLink`).
+// Under hls.js the absence ends when MEDIA arrives again (a fragment loads), not when a session
+// request is answered: a server that answers every session and delivers none of them is still not
+// serving, and ending the absence at each answer restarted the stream forever. What hls.js does not
+// play (a direct file, HLS the browser plays natively) reports no fragments, so there the answer
+// ends it (`answered`); and the viewer trying again after the error starts a window of its own
+// (`start`). The same window bounds a link too slow for the stream (see `slowLink`).
 export const AWAY_WINDOW_MS = 180_000;
 const AWAY_RETRY_MS = [2_000, 4_000, 8_000, 15_000];
 const SERVER_AWAY = new Set([0, 502, 503, 504]);

frontend/src/lib/plexStats.test.ts

@@ -6,6 +6,7 @@ import {
   buildStatRows,
   createFragMeter,
   fmtBitrate,
+  fmtBitrates,
   fmtBufferSecs,
   fmtClock,
   fmtCodec,
@@ -28,6 +29,13 @@ describe("plexStats formatters", () => {
     expect(fmtBitrate(4_200_000, "hu")).toBe("4,2 Mbps"); // the UI language's decimal mark
   });
 
+  it("fmtBitrates says rates side by side in the unit the largest takes", () => {
+    expect(fmtBitrates([1_400_000, 800_000], "en")).toEqual(["1.4 Mbps", "0.8 Mbps"]);
+    expect(fmtBitrates([1_400_000, 800_000], "hu")).toEqual(["1,4 Mbps", "0,8 Mbps"]);
+    expect(fmtBitrates([900_000, 400_000], "en")).toEqual(["900 kbps", "400 kbps"]);
+    expect(fmtBitrates([2_000_000, 0], "en")).toEqual(["2.0 Mbps", DASH]);
+  });
+
   it("fmtBufferSecs shows one decimal, dashes negatives/non-finite", () => {
     expect(fmtBufferSecs(12.34, "en")).toBe("12.3 sec");
     expect(fmtBufferSecs(0, "en")).toBe("0.0 sec");

frontend/src/lib/plexStats.ts

@@ -64,6 +64,16 @@ export function fmtBitrate(bps: number | undefined, lang: string): string {
   return `${formatNumber(Math.round(bps / 1000), lang)} kbps`;
 }
 
+// Rates read side by side ("needs 1.4 Mbps, 0.8 Mbps arrives"): one unit for all of them, the one
+// the largest would take alone, so they compare at a glance — never "1.4 Mbps" beside "800 kbps".
+export function fmtBitrates(rates: number[], lang: string): string[] {
+  const largest = Math.max(0, ...rates);
+  if (largest < 1_000_000) return rates.map((bps) => fmtBitrate(bps, lang));
+  return rates.map((bps) =>
+    bps > 0 ? `${formatDecimal(bps / 1_000_000, lang)} Mbps` : fmtBitrate(bps, lang),
+  );
+}
+
 // Seconds of buffer ahead of the playhead → "12.3 sec" / "12,3 mp".
 export function fmtBufferSecs(s: number, lang: string): string {
   if (!Number.isFinite(s) || s < 0) return DASH;