record_vram_delta() measured free VRAM via _free_vram_snapshot(), which only
read the default CUDA device (device 0). A gpu_split model (e.g. gemma on two
cards) lands most weights on the other card, so the device-0 delta came out
~0, tripped the 'delta <= 0' guard, and never persisted measured_vram_gb. The
estimate stayed 0 and every load OOM-retried from scratch even with
force_vram_update set.

Sum free VRAM across every visible CUDA device (scoped per engine via
CUDA_VISIBLE_DEVICES), plus amdgpu sysfs when cross-pooling is on or no CUDA
device is visible -- mirroring _get_free_vram_gb(). Before/after snapshots are
now symmetric, so the delta captures the full multi-card footprint and the
real value is persisted; subsequent loads size correctly and stop OOM-looping.

Bump version to 0.1.3.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RdMufYvtTbtGDWsiZVoXce