fix(voice): push voice presence to user on mid-session space join

Voice presence (voiceStates/voiceUserStates/spaceVoiceStates) was only ever
delivered in the WS `ready` payload — i.e. at connect/reload. A user joining a
space mid-session got `member_joined` (no voice data) and a bare space object;
`GET /api/spaces/:id` (the channel-sidebar hydrator) carries no voice state
either. So members already sitting in a voice channel stayed invisible in the
new member's sidebar until a full page reload.

Fix at the systemic root: ConnectionManager.addUserSpace — the single chokepoint
every join path funnels through (invite, public join, join-request approval),
and which is NOT used on reconnect (that path uses setUserSpaces) — now pushes a
scoped `space_voice_state` snapshot to the joining user. The snapshot is built by
a new buildSpaceVoiceState(spaceId, userId) helper that is also the single source
of truth feeding buildReadyPayload (refactored to use it), so the connect-time
and join-time paths can never drift.

Robustness:
- Delivered over the same ordered WebSocket as voice_state_update deltas — no
  REST snapshot-vs-event-stream race.
- VIEW_CHANNEL-filtered via computePermissions exactly like `ready`: a joiner is
  never told who occupies a voice channel they cannot see.
- Client applies it scoped to the space (utils/voiceStateSync.applySpaceVoiceState):
  merges occupants/statuses and rebuilds only that space's restriction keys,
  never disturbing voice state in other spaces.
- Skipped when the space has no active voice and no restrictions (e.g. space
  creation).

Tests: server helper behavior, the join push, and private-channel exclusion;
client scoped-apply. Specs updated (websocket.md, voice.md, spaces.md).

packages/web/src/utils/voiceStateSync.test.ts

@@ -0,0 +1,57 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+
+// Stub AudioManager — voiceStore imports it and AudioWorkletNode is absent in jsdom.
+vi.mock('../audio/AudioManager', () => ({
+  AudioManager: {
+    getInstance: vi.fn().mockReturnValue({
+      setInputVolume: vi.fn(),
+      setOutputDevice: vi.fn(),
+      setVolume: vi.fn(),
+    }),
+  },
+}));
+
+import { useVoiceStore } from '../stores/voiceStore';
+import { applySpaceVoiceState } from './voiceStateSync';
+
+beforeEach(() => {
+  useVoiceStore.getState().reset();
+});
+
+describe('applySpaceVoiceState', () => {
+  it('populates voiceUsers, voiceUserStates and scoped restriction sets', () => {
+    applySpaceVoiceState({
+      spaceId: 'sp1',
+      voiceStates: { ch1: ['uA', 'uB'] },
+      voiceUserStates: { uA: { isMuted: true, isDeafened: false, isCameraOn: false, isScreenSharing: false } },
+      spaceVoiceStates: {
+        'sp1:uA': { spaceMuted: true, spaceDeafened: false, permissionMuted: false },
+        'sp1:uB': { spaceMuted: false, spaceDeafened: false, permissionMuted: true },
+      },
+    });
+
+    const s = useVoiceStore.getState();
+    expect(s.getVoiceUsers('ch1')).toEqual(['uA', 'uB']);
+    expect(s.voiceUserStates.get('uA')).toEqual({ isMuted: true, isDeafened: false, isCameraOn: false, isScreenSharing: false });
+    expect(s.spaceMutedUserIds.has('sp1:uA')).toBe(true);
+    expect(s.permissionMutedUserIds.has('sp1:uB')).toBe(true);
+  });
+
+  it('refreshes only its own space, leaving other spaces untouched', () => {
+    useVoiceStore.setState({
+      spaceMutedUserIds: new Set(['sp-other:uX', 'sp1:uStale']),
+    });
+
+    applySpaceVoiceState({
+      spaceId: 'sp1',
+      voiceStates: {},
+      voiceUserStates: {},
+      spaceVoiceStates: { 'sp1:uNew': { spaceMuted: true, spaceDeafened: false, permissionMuted: false } },
+    });
+
+    const s = useVoiceStore.getState();
+    expect(s.spaceMutedUserIds.has('sp-other:uX')).toBe(true);  // untouched
+    expect(s.spaceMutedUserIds.has('sp1:uStale')).toBe(false);  // cleared (authoritative re-sync)
+    expect(s.spaceMutedUserIds.has('sp1:uNew')).toBe(true);
+  });
+});