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/foundation/bitpacker/bitpacker-game/src/interpolation/index.md

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+## Interpolation
+
+**Path:** `src/interpolation/interpolation.ts`  
+**Export:** `GameInterpolator`
+
+### What it does
+
+Advanced interpolation of game state between two points in time. Supports 9 interpolation methods for positions and rotations.
+
+### Methods
+
+| Method | Description |
+|--------|-------------|
+| `LINEAR` | Simple lerp |
+| `CUBIC` | Cubic easing |
+| `HERMITE` | Hermite spline with tension/bias |
+| `CATMULL_ROM` | Catmull-Rom spline |
+| `BEZIER` | Cubic Bezier |
+| `SPRING` | Spring physics |
+| `ELASTIC` | Elastic easing |
+| `BOUNCE` | Bounce easing |
+| `SMOOTHSTEP` | 3t² - 2t³ smoothstep |
+
+### Key API
+
+| Method | Description |
+|--------|-------------|
+| `interpolatePosition(start, end, t, method?)` | Interpolate `Vector3` |
+| `interpolateRotation(start, end, t, method?)` | Interpolate `Rotation` with angle wrapping |
+| `interpolatePlayerState(start, end, t)` | Full player state interpolation |
+| `interpolatePath(points, t, method?)` | Interpolate along a path of points |
+
+### Rotation Handling
+
+Yaw is normalized to `[-180, 180]` and takes the shortest path. Pitch is clamped to `[-90, 90]`.
+
+### Depends on
+
+- `../types.js` — `Vector3`, `Rotation`, `PlayerState`, `InterpolationOptions`

plugins/document-navigator/docs/foundation/bitpacker/bitpacker-game/src/interpolation/interpolation.md

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+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+## interpolation
+
+**Path:** `bitpacker-game/src/interpolation/interpolation.ts`  
+**Export:** See source for details.
+
+### What it does
+
+Part of the @suaveplan/ package.