feat(skill): darwinian-evolver optional skill

Thin wrapper around Imbue's darwinian_evolver (AGPL-3.0, subprocess-only).
Ships a working OpenRouter driver (parrot_openrouter.py), a snapshot
inspector (show_snapshot.py), and a custom-problem template. SKILL.md
has 58-char description, Pitfalls sourced from actually running the loop:
non-viable seed trap, Azure content filter killing runs, loop.run() being
a generator, nested-pickle snapshots, and aggressive default concurrency.

Salvaged from #12719 by @Bihruze — original PR shipped 12,289 LOC across
61 files (29 Python modules, FastAPI dashboard, VS Code extension,
benchmark hub, marketplace, etc.) which was far beyond the scope of the
underlying issue (#336). This version stays at the ~700-LOC scope that
issue actually asked for. Authorship of the original effort credited via
AUTHOR_MAP entry and the SKILL.md author field.

Verified end-to-end: seed 'Say {{ phrase }}' (score 0.000) evolved into
'Please repeat the following phrase exactly as it is, without any
modifications or additional formatting: {{ phrase }}' (score 0.750)
across 3 iterations on gpt-4o-mini via OpenRouter.

Co-authored-by: Bihruze <98262967+Bihruze@users.noreply.github.com>

optional-skills/research/darwinian-evolver/scripts/show_snapshot.py

@@ -0,0 +1,69 @@
+"""
+show_snapshot.py — Dump the population from a darwinian-evolver snapshot pickle.
+
+Usage:
+    python show_snapshot.py PATH/TO/iteration_N.pkl [--field prompt_template]
+
+The script is intentionally Organism-agnostic: it walks `org.__dict__` and prints
+all str fields. By default it shows `prompt_template` if present; pass --field to
+target a different attribute (e.g. `regex_pattern`, `sql_query`, `code_block`).
+"""
+from __future__ import annotations
+
+import argparse
+import pickle
+import sys
+from pathlib import Path
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("snapshot", type=Path)
+    ap.add_argument(
+        "--field",
+        default=None,
+        help="Organism attribute to display. Defaults to the first str field found.",
+    )
+    ap.add_argument("--top", type=int, default=None, help="Show only top N by score.")
+    args = ap.parse_args()
+
+    if not args.snapshot.exists():
+        sys.exit(f"snapshot not found: {args.snapshot}")
+
+    # The outer pickle wraps a dict; the inner pickle contains the actual organism
+    # objects, which must be importable under their original dotted path. If you
+    # ran a custom driver, make sure its module is on sys.path before calling this.
+    outer = pickle.loads(args.snapshot.read_bytes())
+    if not isinstance(outer, dict) or "population_snapshot" not in outer:
+        sys.exit("not a darwinian-evolver snapshot (no population_snapshot key)")
+    inner = pickle.loads(outer["population_snapshot"])
+    pairs = inner["organisms"]  # list of (Organism, EvaluationResult)
+
+    print(f"# organisms: {len(pairs)}\n")
+    ranked = sorted(pairs, key=lambda p: getattr(p[1], "score", 0) or 0, reverse=True)
+    if args.top:
+        ranked = ranked[: args.top]
+
+    for i, (org, res) in enumerate(ranked):
+        score = getattr(res, "score", float("nan"))
+        print(f"=== rank {i} score={score:.3f} ===")
+        # pick field
+        field = args.field
+        if field is None:
+            for k, v in vars(org).items():
+                if isinstance(v, str) and not k.startswith("_") and k not in ("id",):
+                    field = k
+                    break
+        val = getattr(org, field, None) if field else None
+        if val is None:
+            print(f"  (no string field; org fields: {list(vars(org).keys())})")
+        else:
+            print(f"  {field} ({len(val)} chars):")
+            for ln in val.splitlines()[:30]:
+                print(f"    {ln}")
+        print()
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())