fix: limit codec dropdown to codecs the SFU actually accepts

Live-verified via matrix-rtc-sfu negotiation logs (2026-07-28): a real
VP9 publish attempt got "falling back to alternative video codec" -
enabledPublishCodecs was [VP8, H264, H265], no VP9/AV1. The client's
backupCodec masked this (silent regression to VP8, no visible failure),
but offering VP9/AV1 in the dropdown was misleading - selecting them has
no real effect right now. Trimmed the dropdown to VP8/H264/H265 (added
h265 as a real option - livekit-client's own VideoCodec type already
supports it). Also fixed screenShareCodec's default, which was "vp9"
(meaning every user who enabled the toggle without touching the codec
dropdown was silently requesting an unsupported codec) - now "vp8" to
match camera's default.

src/settings/MediaQualitySettings.tsx

@@ -122,15 +122,20 @@ export const MediaQualitySettings: FC<{
             <label htmlFor={`${id}Codec`}>
               {t("settings.codec_label", "Codec")}
             </label>
+            {/* Only list codecs the SFU actually accepts right now (confirmed
+                live via matrix-rtc-sfu negotiation logs, 2026-07-28 -
+                enabledPublishCodecs was [VP8, H264, H265]). VP9/AV1 are not
+                currently negotiated by the SFU - selecting them silently
+                falls back to VP8 via the client's backupCodec, so leaving
+                them out avoids offering a choice that has no real effect. */}
             <select
               id={`${id}Codec`}
               value={codec}
               onChange={(e): void => setCodec(e.target.value as VideoCodec)}
             >
               <option value="vp8">VP8</option>
-              <option value="vp9">VP9</option>
               <option value="h264">H.264</option>
-              <option value="av1">AV1</option>
+              <option value="h265">H.265</option>
             </select>
           </div>
         </>

src/settings/settings.ts

@@ -158,7 +158,7 @@ export const customLivekitUrl = new Setting<string | null>(
   null,
 );
 
-export type VideoCodec = "vp8" | "vp9" | "h264" | "av1";
+export type VideoCodec = "vp8" | "vp9" | "h264" | "av1" | "h265";
 
 /**
  * Parse a "WIDTHxHEIGHT" resolution string into numeric width and height.
@@ -193,7 +193,7 @@ export const screenShareBitrate = new Setting<number>(
 
 export const screenShareCodec = new Setting<VideoCodec>(
   "screen-share-codec",
-  "vp9",
+  "vp8",
 );
 
 // Camera video quality settings