Split the unattended run into a GPU-free phase and a GPU phase

The target machine's card is busy with someone else's job, so a single
end-to-end script stalls on work that does not actually need a GPU.

Compiling the CUDA extensions needs nvcc, not a device, and downloading 18 GB
of data needs neither. Those are the slow parts (~50 min + ~30 min), so phase A
now runs entirely without the card:

  run_setup.sh   bootstrap, conda, extensions, patches, data      no GPU
  run_train.sh   voxel_max measurement, training, evaluation      GPU

run_setup reports the GPU but never fails on it, and verify_env.py gained
SKIP_CUDA_CHECK so import coverage still runs when no device is visible.
TORCH_CUDA_ARCH_LIST is stated rather than probed, since the card may be
unavailable at build time.

run_train waits for the GPU instead of failing when it is busy: it polls until
enough VRAM frees up (12h default), so it can be queued ahead of time. Past the
deadline it proceeds anyway and lets the measured voxel_max adapt to whatever
is actually free.

keepalive.sh now takes the phase to supervise. Replaces run_all.sh and RUN.md
with SETUP.md and TRAIN.md. Adds selfcheck.sh, which syntax-checks every script
and flags CRLF endings - a shell script with either fails at its first line,
which for an unattended weekend run means losing the weekend.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/selfcheck.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# SUM Parts - syntax-check every script in this directory
+#
+# Cheap guard: a shell script with a syntax error fails at the first line it
+# reaches, which for an unattended weekend run means losing the weekend.
+set -uo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")"
+
+fail=0
+
+echo "=== bash ==="
+for f in *.sh; do
+    printf '  %-26s' "$f"
+    if bash -n "$f" 2>/dev/null; then echo "OK"; else echo "SYNTAX ERROR"; fail=1; fi
+done
+
+echo
+echo "=== python ==="
+for f in *.py; do
+    printf '  %-26s' "$f"
+    if python3 -c "import ast,sys; ast.parse(open(sys.argv[1],encoding='utf-8').read())" "$f" 2>/dev/null
+    then echo "OK"; else echo "SYNTAX ERROR"; fail=1; fi
+done
+
+echo
+echo "=== CRLF check (breaks bash on Linux) ==="
+if grep -rlU $'\r' ./*.sh ./*.py 2>/dev/null; then
+    echo "  ^ these have CRLF line endings and will fail with: bash: \$'\\r': command not found"
+    fail=1
+else
+    echo "  clean"
+fi
+
+echo
+[ "$fail" -eq 0 ] && echo "ALL OK" || echo "PROBLEMS FOUND"
+exit "$fail"