feat: add containerized training workflow

- add a GPU trainer Compose profile with mounted data, models, and checkpoints
- add host commands for preflight, lifecycle, logs, status, and checkpoint cleanup
- resume from the latest complete checkpoint with external config or CLI arguments

scripts/docker/train-entrypoint.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/lib/train-common.sh"
+
+TRAIN_JOB_NAME="${TRAIN_JOB_NAME:?TRAIN_JOB_NAME is required}"
+CHECKPOINT_ROOT="${CHECKPOINT_ROOT:-/checkpoints}"
+CHECKPOINT_DIR="${CHECKPOINT_ROOT}/${TRAIN_JOB_NAME}"
+BASE_MODEL="${BASE_MODEL:-/models/base}"
+TRAIN_CONFIG="${TRAIN_CONFIG:-}"
+TRAIN_GPU_COUNT="${TRAIN_GPU_COUNT:-all}"
+
+validate_job_name "${TRAIN_JOB_NAME}"
+if [[ "${TRAIN_GPU_COUNT}" == "all" ]]; then
+    TRAIN_GPU_COUNT="$(python -c 'import torch; print(torch.cuda.device_count())')"
+fi
+[[ "${TRAIN_GPU_COUNT}" =~ ^[1-9][0-9]*$ ]] || die "No visible GPU found"
+if [[ -n "${TRAIN_CONFIG}" ]]; then
+    [[ -f "${TRAIN_CONFIG}" ]] || die "Training config not found: ${TRAIN_CONFIG}"
+fi
+[[ -r /data ]] || die "Training data directory is not readable: /data"
+
+mkdir -p "${CHECKPOINT_DIR}"
+[[ -w "${CHECKPOINT_DIR}" ]] || die "Checkpoint directory is not writable: ${CHECKPOINT_DIR}"
+
+latest_checkpoint="$(find_latest_checkpoint "${CHECKPOINT_DIR}" || true)"
+
+train_args=(
+    python scripts/tools/train.py
+    --ckpt_dir "${CHECKPOINT_DIR}"
+    --nprocs "${TRAIN_GPU_COUNT}"
+)
+
+if [[ -n "${TRAIN_CONFIG}" ]]; then
+    train_args+=(--config "${TRAIN_CONFIG}")
+fi
+
+if (( TRAIN_GPU_COUNT > 1 )); then
+    train_args+=(--parallel_mode ddp)
+else
+    train_args+=(--parallel_mode none)
+fi
+
+if [[ -n "${latest_checkpoint}" ]]; then
+    log_info "Resuming ${TRAIN_JOB_NAME} from ${latest_checkpoint}"
+    train_args+=(--param_path "${latest_checkpoint}" --resume)
+else
+    [[ -s "${BASE_MODEL}/config.json" ]] || die "Base model config not found: ${BASE_MODEL}/config.json"
+    [[ -s "${BASE_MODEL}/model.safetensors" ]] || die "Base model weights not found: ${BASE_MODEL}/model.safetensors"
+    log_info "Starting ${TRAIN_JOB_NAME} from ${BASE_MODEL}"
+    train_args+=(--param_path "${BASE_MODEL}")
+fi
+
+log_info "GPUs=${TRAIN_GPU_COUNT}, checkpoints=${CHECKPOINT_DIR}"
+
+# Replace the shell so the container init forwards SIGTERM to the trainer.
+exec "${train_args[@]}" "$@"