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/media/audio-fx/audio-fx-plugin-flanger/README.md

@@ -0,0 +1,31 @@
+# @suaveplan/audio-fx-plugin-flanger - flanger plugin for the @suaveplan/audio-fx-plugin-* family.
+
+flanger plugin for the @suaveplan/audio-fx-plugin-* family.
+
+Member of the `@suaveplan/audio-fx-plugin-*` family. Universal (browser / server / offline / worklet identical). Depends on `@suaveplan/audio-fx-plugin-base` for the `AudioFxPlugin` contract; declares no other `@suaveplan/audio-fx-plugin-*` deps.
+
+<!-- begin:auto-docs -->
+## Documentation tree
+
+- [flanger](./src/flanger/flanger.md) — `FlangerPlugin` is the universal comb-filter flanger. A short LFO-modulated delay line (sub-10 ms) is summed with the d…
+  - [flanger](./src/flanger/flanger.md) — `FlangerPlugin` is the universal comb-filter flanger. A short LFO-modulated delay line (sub-10 ms) is summed with the d…
+- [schemas](./src/schemas/schemas.md) — Zod schemas validating the construction-time options and preset payload of `FlangerPlugin`. These run on the public bou…
+  - [schemas](./src/schemas/schemas.md) — Zod schemas validating the construction-time options and preset payload of `FlangerPlugin`. These run on the public bou…
+<!-- end:auto-docs -->
+
+## Composition
+
+```ts
+import { PluginChain, DefaultBusRegistry } from "@suaveplan/audio-fx-plugin-base/chain";
+import { /* Plugin */ } from "@suaveplan/audio-fx-plugin-flanger";
+
+const plugin = new /* Plugin */();
+const chain = new PluginChain({
+ buses: new DefaultBusRegistry(),
+ plugins: [plugin],
+});
+```
+
+## Status
+
+Replaces the `./flanger` subpath of the bundled `@suaveplan/audio-plugins-fx`.