Unify dataset/tooling scripts into a single dwarf Typer CLI

Replace the five separately-hyphenated uv entry points (steps-to-parquet,
steps-to-parquet-parallel, migrate-geant-steps, bump-dataset-version,
create-root-files) plus the unregistered hparam_scan.py with one `dwarf`
command exposing convert/migrate/bump-gen/bump-schema/status/
update-manifest/create-manifest/make-root/hparam-scan as subcommands.

Each scripts/*.py module now only holds argparse-free business logic;
scripts/dwarf.py wires it up with Typer, matching giant/cli.py's style.
`dwarf convert` merges the old serial/parallel conversion scripts behind
a --jobs flag (default 1: sequential with plain -o; >1: dataset-layout
fan-out via subprocess).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/hparam_scan.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 """Hyperparameter scan over dropout x n_blocks x hidden_dim.
 
 Runs `giant train` sequentially (this machine has a single GPU) for every
@@ -6,13 +5,9 @@ combination, plus one extra run at the default architecture with a higher
 learning rate. Runs are shuffled so the parameter space gets coarse coverage
 early rather than exhausting one corner of the grid first.
 
-Usage:
-    uv run python scripts/hparam_scan.py
-    uv run python scripts/hparam_scan.py --dry-run
-    uv run python scripts/hparam_scan.py --seed 1 --data /path/to/parquet
+See `uv run dwarf hparam-scan --help` for the CLI.
 """
 
-import argparse
 import csv
 import itertools
 import os
@@ -87,31 +82,29 @@ def append_summary(summary_path: Path, row: dict) -> None:
         writer.writerow(row)
 
 
-def main() -> None:
-    parser = argparse.ArgumentParser(description=__doc__)
-    parser.add_argument("--data", default=DATA_DEFAULT)
-    parser.add_argument("--scan-dir", default=SCAN_DIR_DEFAULT)
-    parser.add_argument("--seed", type=int, default=0)
-    parser.add_argument("--dry-run", action="store_true")
-    args = parser.parse_args()
+def run_hparam_scan(
+    data: str = DATA_DEFAULT,
+    scan_dir: str = SCAN_DIR_DEFAULT,
+    seed: int = 0,
+    dry_run: bool = False,
+) -> None:
+    runs = build_runs(seed)
+    scan_dir_path = Path(scan_dir)
 
-    runs = build_runs(args.seed)
-    scan_dir = Path(args.scan_dir)
-
-    if args.dry_run:
+    if dry_run:
         for i, run in enumerate(runs, 1):
             print(f"[{i}/{len(runs)}] {run_name(run)}")
         return
 
-    scan_dir.mkdir(parents=True, exist_ok=True)
-    summary_path = scan_dir / "scan_summary.csv"
+    scan_dir_path.mkdir(parents=True, exist_ok=True)
+    summary_path = scan_dir_path / "scan_summary.csv"
 
     env = os.environ.copy()
     env["TQDM_DISABLE"] = "1"
 
     for i, run in enumerate(runs, 1):
         name = run_name(run)
-        out_dir = scan_dir / name
+        out_dir = scan_dir_path / name
         metrics_path = out_dir / "metrics.csv"
         last_ckpt = out_dir / "last.pt"
 
@@ -124,7 +117,7 @@ def main() -> None:
         cmd = [
             "giant",
             "train",
-            args.data,
+            data,
             "--mode",
             "flow",
             "--epochs",
@@ -186,7 +179,3 @@ def main() -> None:
             print(
                 f"[{i}/{len(runs)}] {name} — no metrics.csv produced, check train.log"
             )
-
-
-if __name__ == "__main__":
-    main()