Move docs/ package mirror into document-navigator plugin

Relocate the ~6k-file docs tree from the repo root into
plugins/document-navigator/docs/ so the plugin is self-contained and
portable. docs/superpowers/ (specs and plans) stays at the repo root.

Moved via cp+rm rather than git mv because directory rename() fails with
EPERM on this WSL /mnt DrvFs mount; git rename-detection pairs the
identical-content files at commit time.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/document-navigator/docs/ui/react/react-audio-stream/src/test-utils.md

@@ -0,0 +1,65 @@
+# test-utils
+
+## Purpose
+
+`test-utils.tsx` provides the in-memory `FakeSession` and the `withProvider` wrapper used
+by every chunk-C hook + component test. The fake mirrors the canonical `StreamSessionLike`
+contract from the spec — same method names, same event channels — so tests exercise the
+real React render path without booting transports or audio engines. Tests inject the
+fake via the provider's `sessionFactory`, drive state mutations through the public API,
+and assert the rendered DOM, hook return value, and recorded method calls.
+
+The file lives at the package root rather than inside a feature directory because it is
+shared by every feature module; `vitest.config.ts` excludes it from coverage.
+
+## Features
+
+- `FakeSession` — `StreamSessionLike` implementation with synchronous mutators, an
+  internal `calls` recorder, and helpers (`pushPeer`, `setMixer`, `triggerInterruption`)
+  that emit the matching event channel.
+- `withProvider(session)` — returns a `wrapper` suitable for
+  `renderHook`/`render({ wrapper })`.
+- Strongly typed: every method signature matches the canonical spec so a compile-time
+  break in chunks A+B surfaces here first.
+
+## Usage: Basic
+
+```tsx
+import { renderHook } from "@testing-library/react";
+import { FakeSession, withProvider } from "../../test-utils.js";
+import { useStreamSession } from "./use-stream-session.js";
+
+const session = new FakeSession();
+const { result } = renderHook(() => useStreamSession(), {
+    wrapper: withProvider(session),
+});
+```
+
+## Usage: Advanced
+
+```tsx
+const session = new FakeSession({
+    state: "joined",
+    peers: [{ id: "alice", displayName: "Alice", connectionState: "connected", rttMs: 32 }],
+});
+// Drive state changes deterministically:
+await act(async () => session.pushPeer({ id: "bob", ... }));
+expect(result.current.peers).toHaveLength(2);
+expect(session.calls.setTrackVolume).toEqual([["alice", -3]]);
+```
+
+## API Reference
+
+- `FakeSessionInit` — constructor options bag.
+- `FakeSession` — `StreamSessionLike` plus `calls`, `pushPeer`, `setPeers`, `setMixer`,
+  `setLocalLevel`, `setPeerLevel`, `triggerInterruption`.
+- `withProvider(session)` — `(props: { children }) => ReactNode`.
+
+## Implementation Notes
+
+The fake's event-emit path is synchronous (no microtask hop) so test assertions can run
+immediately after the mutation without `act` for simple cases. When tests need to
+observe a React re-render fence, they wrap the mutator in `act(() => session.foo())`.
+The recorded `calls` arrays let solo-semantics tests verify that mutations route through
+the session's `setTrackVolume` / `setTrackMute` / `setTrackSolo` rather than being
+re-implemented inside the hook.