Hands: the hand recorder's window, review and export

hands/rec/ft_handrec.py + main.qml (Kirigami, dev container; host launcher
hands/rec/ft-handrec): consent (CONSENT.md, asked again when its version
changes; profile.json with a random contributor id), the before-you-start
checklist with the lighting and free-space checks, the session controls
(Space pauses, Esc stops), review with a frame-set viewer that deletes
ranges, takes and sessions, export with progress and cancel (warns while
the headset is worn), and the upload page (UPLOAD.md, the
huggingface-cli command; HF_DATASET is a placeholder). --dry-run runs
sessions without processes, for testing.

hands/rec/takes.py (standard library): indexes sets.bin and sets-N.bin
without reading pixels, reads one set's cameras, keeps deleted ranges in
take.json, and exports: deleted sets left out, zstd -10 -T2 at nice 19,
manifest.json and SHA256SUMS, nothing left behind on cancel.

CONSENT.md and UPLOAD.md are drafts pending a legal review; the window
says contributions aren't open yet. The dev container gains zstd.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

setup/dev-container.sh

@@ -23,6 +23,8 @@ packages=(
   # tools (hands/tools) need NumPy and OpenCV, which aren't here: Fedora's python3-opencv pulls
   # in over a gigabyte (hands/README.md says how to get them)
   jsoncpp-devel glibc-static
+  # hand recorder (hands/rec): its export compresses recordings with zstd
+  zstd
   # Frametop Input Settings app (Kirigami, PySide6)
   python3-pyside6 kf6-kirigami kf6-qqc2-desktop-style qt6-qtwayland breeze-icon-theme plasma-breeze
   # Frametop remote desktop (VNC bridge through krdp)