fix(web): extract cross-store resolvers into neutral utility to break TDZ

instanceStore registers three resolver functions at module load —
setApiForOriginResolver, setUserIdForOriginResolver,
setOriginFromHostnameResolver — whose backing `let` bindings used to
live in spaceStore. When the module graph was entered from
instanceStore (e.g. JoinSpaceModal importing useInstanceStore) the
order became spaceStore → chatStore → useWebSocket → socialStore →
instanceStore (top-level setter call) while spaceStore was still
paused on its line-8 chatStore import, so the backing `let` had not
been reached yet and the setter crashed with
`Cannot access '_getApiForOrigin' before initialization`. This left
InviteModal.test.tsx and JoinSpace.test.tsx unable to even load their
suites once AudioManager was mocked away.

Move the three `let` bindings, their setters, their pure getters, plus
the WS-populated user-ID cache (`_myUserIdByOrigin`, setMyUserIdForOrigin,
getCachedUserIdForOrigin, clearMyUserIdCache) into
`packages/web/src/utils/crossStoreResolvers.ts`. The utility imports
nothing from `./stores/*`, so no back-edge exists. spaceStore re-exports
the public surface for backward compatibility with the many existing
import sites; instanceStore imports the setters directly from the
utility (the in-cycle re-export path does not resolve at module-init
time under vite-ssr, so a direct import is required for the top-level
setter calls).

spaceStore's remaining wrappers (resolveUserOrigin, getLayoutHomeOrigin,
getMyUserIdForOrigin) stay where they are — they combine the utility's
pure lookups with authStore state — but now delegate to the utility.

Also adds the AudioManager mock to InviteModal.test.tsx and
JoinSpace.test.tsx so their suites actually load (same pattern already
used in 5 other test files). Net test-suite result: 127/131 pass (up
from 121/121 — +6 newly unlockable). The 4 remaining JoinSpace
failures are pre-existing stale UI-text assertions (the placeholder was
expanded and the submit button was made disable-when-empty) made
visible by the suite now loading; they're orthogonal to this change
and handed back for a separate triage.

Closes backlog #27.

packages/web/src/components/modals/InviteModal.test.tsx

@@ -1,6 +1,18 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { render, screen, waitFor } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
+
+// Stub AudioManager to avoid AudioWorkletNode reference error in jsdom.
+// Reached transitively via spaceStore → chatStore → useWebSocket → voiceStore.
+vi.mock('../../audio/AudioManager', () => ({
+  AudioManager: {
+    getInstance: vi.fn().mockReturnValue({
+      setOutputDevice: vi.fn(),
+      setVolume: vi.fn(),
+    }),
+  },
+}));
+
 import { InviteModal } from './InviteModal';
 import { useUIStore } from '../../stores/uiStore';
 import { useSpaceStore } from '../../stores/spaceStore';

packages/web/src/components/modals/JoinSpace.test.tsx

@@ -2,6 +2,18 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { render, screen, waitFor } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
 import { MemoryRouter } from 'react-router-dom';
+
+// Stub AudioManager to avoid AudioWorkletNode reference error in jsdom.
+// Reached transitively via spaceStore → chatStore → useWebSocket → voiceStore.
+vi.mock('../../audio/AudioManager', () => ({
+  AudioManager: {
+    getInstance: vi.fn().mockReturnValue({
+      setOutputDevice: vi.fn(),
+      setVolume: vi.fn(),
+    }),
+  },
+}));
+
 import { JoinSpaceModal } from './JoinSpace';
 import { useUIStore } from '../../stores/uiStore';
 import { useSpaceStore } from '../../stores/spaceStore';