feat: just dyn = auto-plot newest full-length log per arm

--latest-per-arm + --min-steps select the freshest >=N-step log for each
arm from logs/, no hand-globbing. Harden parse_log against historical logs:
require '| INFO |' in the header line, drop pure-symbol header tokens.

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

scripts/plot_dynamics.py

@@ -87,10 +87,13 @@ def parse_log(path: Path) -> dict | None:
     vhack = grab(r"v-hack-path=out/(?:vhack/)?(\S+?)\.safetensors", argv, "-")
 
     # header line: the one containing both "step" and "hack_s"
-    hdr = next((l for l in txt.splitlines() if "ref_eq" in l and "hack_s" in l), None)
+    hdr = next((l for l in txt.splitlines()
+                if "| INFO |" in l and "ref_eq" in l and "hack_s" in l), None)
     if hdr is None:
         return None
-    names = [_HDR_TOK.match(t).group(0) for t in hdr.split("| INFO |", 1)[1].split()]
+    # real column headers always start with a letter/underscore; drop pure-symbol
+    # tokens (decoration) so a stray glyph in an old log's header doesn't crash parse
+    names = [m.group(0) for t in hdr.split("| INFO |", 1)[1].split() if (m := _HDR_TOK.match(t))]
     idx = {n: i for i, n in enumerate(names)}
 
     series: dict[str, list[float]] = defaultdict(list)
@@ -330,13 +333,33 @@ def _gather(paths: list[str]) -> list[Path]:
     return out
 
 
+def _latest_per_arm(files: list[Path], min_steps: int) -> list[Path]:
+    """One log per arm: the most recent (by filename timestamp) with >= min_steps
+    rows. Lets `just dyn` auto-pick the freshest full-length run for each arm
+    instead of hand-globbing. Newest filename wins -- timestamp-prefixed names
+    sort lexicographically, no mtime races."""
+    by_arm: dict[str, tuple[Path, dict]] = {}
+    for f in sorted(files):  # ascending ts; later overwrites -> keeps newest
+        r = parse_log(f)
+        if r is None or len(r["steps"]) < min_steps:
+            continue
+        by_arm[classify(r)] = (f, r)
+    return [f for f, _ in by_arm.values()]
+
+
 def main() -> None:
     ap = argparse.ArgumentParser(description=__doc__)
     ap.add_argument("logs", nargs="+", help="log files, globs, or dirs")
     ap.add_argument("--out", type=Path, default=Path("out/figs/dynamics.png"))
+    ap.add_argument("--latest-per-arm", action="store_true",
+                    help="keep only the newest log per arm (with >= --min-steps rows)")
+    ap.add_argument("--min-steps", type=int, default=0,
+                    help="drop runs shorter than this many logged steps")
     args = ap.parse_args()
     files = _gather(args.logs)
-    runs = [r for f in files if (r := parse_log(f))]
+    if args.latest_per_arm:
+        files = _latest_per_arm(files, args.min_steps)
+    runs = [r for f in files if (r := parse_log(f)) and len(r["steps"]) >= args.min_steps]
     if not runs:
         raise SystemExit(f"no parseable runs in {len(files)} files")
     for r in runs: