feat(call): in-call soundboard, quality controls, room call-permissions

Element Call is now consumed as our self-built fork
(@lotusguild/element-call-embedded); wire up its previously-dormant
capabilities and document the fork as live.

Soundboard (P5-15): a call-bar button plays user-uploaded audio clips into the
call as a real published track (io.lotus.inject_audio) plus local playback.
Clips are uploadable like emoji/sticker packs, stored in io.lotus.soundboard
account data (synced across devices). Gated by a Settings toggle + volume.

Quality controls (P5-31): per-user mic/screenshare bitrate + screenshare
framerate (Settings -> Calls), applied via io.lotus.set_quality clamped to any
room cap. Room admins set caps and hard call-permissions (allow_screenshare /
allow_camera) in Room Settings -> Voice; the call bar hides blocked buttons.

- New: CallSoundboard, useSoundboard, soundboardClips; RoomQuality,
  useCallQuality, callQuality (+ unit tests).
- Optimistic-write RoomQuality admin UI (no stale-state clobber).
- Docs: mark EC fork live across README/FEATURES/TODO/BUGS/TESTING; add D2
  manual-test steps.

Numeric quality caps are client-cooperative; screenshare/camera permissions are
hard-enforced server-side (see LotusGuild/matrix voice-limit-guard).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/common-settings/general/RoomQuality.tsx

@@ -0,0 +1,198 @@
+import React, { useCallback, useEffect, useMemo, useState } from 'react';
+import { Box, Switch, Text } from 'folds';
+import { SequenceCard } from '../../../components/sequence-card';
+import { SequenceCardStyle } from '../../room-settings/styles.css';
+import { SettingTile } from '../../../components/setting-tile';
+import { SettingsSelect } from '../../../components/settings-select/SettingsSelect';
+import { useMatrixClient } from '../../../hooks/useMatrixClient';
+import { useRoom } from '../../../hooks/useRoom';
+import { StateEvent } from '../../../../types/matrix/room';
+import { useStateEvent } from '../../../hooks/useStateEvent';
+import { RoomPermissionsAPI } from '../../../hooks/useRoomPermissions';
+import { AsyncStatus, useAsyncCallback } from '../../../hooks/useAsyncCallback';
+import {
+  AUDIO_BITRATE_OPTIONS,
+  RoomQualityContent,
+  SCREENSHARE_BITRATE_OPTIONS,
+  SCREENSHARE_FRAMERATE_OPTIONS,
+} from '../../../utils/callQuality';
+
+// Only the numeric cap keys are edited via `update`; the boolean policy keys
+// are handled by `setAllow`.
+type CapKey = 'audio_max_kbps' | 'screenshare_max_kbps' | 'screenshare_max_fps';
+
+// String <-> numeric bridge for SettingsSelect (which needs string values).
+const toValue = (n?: number): string => (typeof n === 'number' ? String(n) : 'auto');
+
+const CAP_KEYS: (keyof RoomQualityContent)[] = [
+  'audio_max_kbps',
+  'screenshare_max_kbps',
+  'screenshare_max_fps',
+  'allow_screenshare',
+  'allow_camera',
+];
+const capsEqual = (a: RoomQualityContent, b: RoomQualityContent): boolean =>
+  CAP_KEYS.every((k) => a[k] === b[k]);
+
+type RoomQualityProps = {
+  permissions: RoomPermissionsAPI;
+};
+/**
+ * [P5-31] Room-admin quality ceiling. Writes `io.lotus.room_quality`; every
+ * Lotus client clamps its per-user quality to these caps. Hard enforcement for
+ * ALL Matrix clients is a server-side follow-up (see LOTUS_TODO.md P5-31).
+ */
+export function RoomQuality({ permissions }: RoomQualityProps) {
+  const mx = useMatrixClient();
+  const room = useRoom();
+
+  const canEdit = permissions.stateEvent(StateEvent.LotusRoomQuality, mx.getSafeUserId());
+
+  const event = useStateEvent(room, StateEvent.LotusRoomQuality);
+  const caps = useMemo<RoomQualityContent>(() => event?.getContent() ?? {}, [event]);
+
+  const [submitState, submit] = useAsyncCallback(
+    useCallback(
+      async (next: RoomQualityContent) => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        await mx.sendStateEvent(room.roomId, StateEvent.LotusRoomQuality as any, next);
+      },
+      [mx, room.roomId],
+    ),
+  );
+  const submitting = submitState.status === AsyncStatus.Loading;
+
+  // Optimistic mirror: `useStateEvent` only refreshes when the write echoes
+  // back via /sync (not when sendStateEvent resolves), so consecutive edits
+  // must build on the pending write — otherwise a second edit spreads a stale
+  // `caps` and silently drops the first. `effective` is what the UI shows and
+  // what each edit merges into; it's reconciled below once the echo lands.
+  const [pending, setPending] = useState<RoomQualityContent | null>(null);
+  const effective = pending ?? caps;
+
+  useEffect(() => {
+    if (!pending) return;
+    // Revert the optimistic view if the write failed…
+    if (submitState.status === AsyncStatus.Error) {
+      setPending(null);
+      return;
+    }
+    // …or drop it once the synced state actually reflects it.
+    if (capsEqual(caps, pending)) setPending(null);
+  }, [caps, pending, submitState.status]);
+
+  const commit = (next: RoomQualityContent) => {
+    setPending(next);
+    submit(next);
+  };
+
+  const update = (key: CapKey, value: string) => {
+    const next: RoomQualityContent = { ...effective };
+    if (value === 'auto') delete next[key];
+    else next[key] = parseInt(value, 10);
+    commit(next);
+  };
+
+  const setAllow = (key: 'allow_screenshare' | 'allow_camera', allowed: boolean) => {
+    const next: RoomQualityContent = { ...effective };
+    // Absent = allowed, so only persist the key when forbidding.
+    if (allowed) delete next[key];
+    else next[key] = false;
+    commit(next);
+  };
+
+  // Absent/true = allowed.
+  const screenshareAllowed = effective.allow_screenshare !== false;
+  const cameraAllowed = effective.allow_camera !== false;
+
+  return (
+    <SequenceCard
+      className={SequenceCardStyle}
+      variant="SurfaceVariant"
+      direction="Column"
+      gap="400"
+    >
+      <SettingTile
+        title="Call Permissions"
+        description={
+          <Text size="T200" priority="300">
+            Control what participants may share in this room. These are enforced on the server for
+            every Matrix client (Element, FluffyChat, Lotus Chat, …).
+          </Text>
+        }
+      />
+      <Box direction="Column" gap="300">
+        <SettingTile
+          title="Allow Screen Sharing"
+          description="When off, no one can share their screen in this room."
+          after={
+            <Switch
+              variant="Primary"
+              value={screenshareAllowed}
+              onChange={(v) => setAllow('allow_screenshare', v)}
+              disabled={!canEdit || submitting}
+            />
+          }
+        />
+        <SettingTile
+          title="Allow Camera"
+          description="When off, this is an audio-only room — no one can turn on their camera. Microphones are always allowed."
+          after={
+            <Switch
+              variant="Primary"
+              value={cameraAllowed}
+              onChange={(v) => setAllow('allow_camera', v)}
+              disabled={!canEdit || submitting}
+            />
+          }
+        />
+      </Box>
+
+      <SettingTile
+        title="Call Quality Caps"
+        description={
+          <Text size="T200" priority="300">
+            Set a maximum microphone bitrate, screenshare bitrate, and screenshare framerate for
+            this room. Lotus Chat clamps each participant to these ceilings (best-effort — applies
+            to Lotus Chat clients). Auto = no cap.
+          </Text>
+        }
+      />
+      <Box direction="Column" gap="300">
+        <SettingTile
+          title="Max Microphone Bitrate"
+          after={
+            <SettingsSelect
+              value={toValue(effective.audio_max_kbps)}
+              onChange={(v) => update('audio_max_kbps', v)}
+              options={AUDIO_BITRATE_OPTIONS}
+              disabled={!canEdit || submitting}
+            />
+          }
+        />
+        <SettingTile
+          title="Max Screenshare Bitrate"
+          after={
+            <SettingsSelect
+              value={toValue(effective.screenshare_max_kbps)}
+              onChange={(v) => update('screenshare_max_kbps', v)}
+              options={SCREENSHARE_BITRATE_OPTIONS}
+              disabled={!canEdit || submitting}
+            />
+          }
+        />
+        <SettingTile
+          title="Max Screenshare Framerate"
+          after={
+            <SettingsSelect
+              value={toValue(effective.screenshare_max_fps)}
+              onChange={(v) => update('screenshare_max_fps', v)}
+              options={SCREENSHARE_FRAMERATE_OPTIONS}
+              disabled={!canEdit || submitting}
+            />
+          }
+        />
+      </Box>
+    </SequenceCard>
+  );
+}

src/app/features/common-settings/general/index.ts

@@ -4,6 +4,7 @@ export * from './RoomHistoryVisibility';
 export * from './RoomJoinRules';
 export * from './RoomProfile';
 export * from './RoomPublish';
+export * from './RoomQuality';
 export * from './RoomShareInvite';
 export * from './RoomUpgrade';
 export * from './RoomVoiceLimit';