feat(director): recorded camera tracks and shot lens (scene document v7)

Scene documents gain a second kind of explicit move: `move.track`, timed
samples of position, orientation and an optional 35 mm-equivalent focal
length. Playback, Load, Replay and seek share one sampler, which stretches
the recording to the shot's duration (so editing durationSec retimes a
take), takes the short arc for longitude/heading/roll and returns recorded
samples exactly. Tracks require the ellipsoid altitude reference and are
bounded to 10,000 samples.

Shots may also carry a `lens`: focal length and a thin-lens depth of field
whose distances are divided by a miniature scale, so a 1:1000 rig renders
the city like a tabletop model. A new camera-lens owner applies it to the
frustum and a depth-of-field post-process stage; shots without a lens
restore the default view. SceneDirector accepts the lens as an injected
dependency, captures a changed lens with a shot and gains addRecordedShot()
for takes. Versions 1-6 import unchanged.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015H1iLusTzWpVKitGic2AW8

docs/SCENE-DOCUMENT.md

@@ -103,3 +103,8 @@ change with this document boundary.
 Version 5 additionally accepts scene `dataPacks` and shot `dataPackIds`, as
 defined in [data packs](DIRECTOR-DATA-PACKS.md). Version-4 camera documents
 continue to import without adding any packs.
+
+Version 7 is the write format. It additionally accepts recorded camera tracks
+(`move.track`) and an optional shot `lens` (focal length and depth of field), as
+defined in [camera directions](DIRECTOR-CAMERA.md#recorded-tracks). Versions 1
+to 6 import unchanged; their shots receive no lens and keep the default view.