Re-apply the subcommand restructure that was lost during the earlier
rebase conflict (the linter pre-commit on the remote re-formatted the
single-function version, so my checkout --ours kept the wrong copy).
Adds:
* argparse subcommands `train` and `reload --format X --dir D` so
each reload runs in a FRESH Python process the way real users
hit the cold-start path.
* Per-phase Phase() context manager records elapsed wall-clock,
peak GPU memory (mx.metal.get_peak_memory), and peak RSS
(resource.getrusage) into a metrics dict written to
{train,lora_reload,merged_reload,gguf_reload}_metrics.json
next to the saved dir for cross-CI regression detection.
* batch_size=2, gradient_accumulation_steps=3 (was 2/1) so the
7-step run sees 42 sequences total.
* GGUF save is best-effort. unsloth-zoo#627 fixed the
NotImplementedError on Apple Silicon, but llama.cpp's
convert_hf_to_gguf currently asserts on the gemma-3-270m
tokenizer vocab (`max(vocab IDs) >= vocab_size`). That's a
downstream llama.cpp limitation, not an unsloth_zoo bug, so the
train step records gguf_supported=false + the reason instead of
raising, and the GGUF reload step emits a workflow warning and
exits 0. The LoRA + merged_16bit reload assertions remain the
gating signal.
The earlier-draft LoRA workaround that copied base config.json into
the LoRA save dir is removed; unsloth-zoo#627 makes
FastMLXModel.from_pretrained(lora_dir) work on the saved adapter
directory directly (the failing run before #627 confirmed the bug,
the run after #627 lands shows the adapter is detected and the base
model is pulled from adapter_config.json:base_model_name_or_path).