feat(config/scripts): GREEN config wiring + S6 recompute tooling

prod/configs/green.yml:
- asset_bucket_ban_set: [4] (B4 banned at selector level)
- s6_size_table: inline bootstrap multipliers (B0→0.4, B1→0.3, B3→2.0,
  B5→0.5, B6→1.5) matching CRITICAL_ASSET_PICKING S6 scenario
- esof_sizing_table: FAV→1.2, MILD_POS→0.6, UNKNOWN→0.25,
  MILD_NEG→0.0, UNFAV→0.0
- use_int_leverage: true (1x fixed pending winrate analysis)
- s6_table_path: pointer to generated YAML (recompute updates this)
BLUE (blue.yml) carries none of these keys → BLUE math unchanged.

prod/configs/green_s6_table.yml: bootstrap stub with frontmatter
(generated_at, source_branch, n_trades). Regenerated by recompute script.

prod/scripts/recompute_s6_coefficients.py:
  Queries trade_events, maps assets to KMeans buckets, derives per-bucket
  sizing mults. Variance guard: >20% net-PnL move flags bucket in
  dolphin.s6_recompute_log for manual review before promote.

prod/s6_recompute_flow.py:
  Prefect flow wrapping the recompute script. Cadence via
  S6_RECOMPUTE_INTERVAL_DAYS env (default 30). Kill-switch:
  S6_RECOMPUTE_DISABLED=1.

prod/scripts/analyze_leverage_winrate.py:
  Read-only walk of CH trade_events; bins trades by leverage_raw,
  emits per-bin WR/net-PnL/avg-MAE. Output informs the int-leverage
  rounding rule choice (Option 1 round-half-up vs Option 2 banker's round
  vs stay-at-1x). Does not auto-apply a rule change.

Plan refs: Tasks 3, 8, 10.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prod/s6_recompute_flow.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""Prefect flow — periodically recompute S6 bucket sizing coefficients.
+
+Cadence
+───────
+Controlled by env `S6_RECOMPUTE_INTERVAL_DAYS` (default 30). The flow is
+idempotent: running it more often than the interval just produces a fresh
+YAML and markdown report; nothing is auto-promoted.
+
+Kill-switch
+───────────
+Set env `S6_RECOMPUTE_DISABLED=1` to skip — the flow logs and exits 0.
+
+Wiring into supervisord/cron
+────────────────────────────
+Run this flow on the supervisord host. Recommended: daily timer that guards
+internally on the last-run timestamp in `dolphin.s6_recompute_log`, or a
+Prefect deployment with a cron schedule `0 3 * * *` and the interval env set.
+
+This flow shells out to `prod/scripts/recompute_s6_coefficients.py` rather
+than importing it so that the script remains independently runnable without
+requiring Prefect — honours the plan's "recompute works whether or not
+Prefect is installed" requirement.
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+from datetime import datetime, timedelta
+from pathlib import Path
+
+try:
+    from prefect import flow, task, get_run_logger
+except ImportError:  # pragma: no cover — allow import-only smoke tests
+    def flow(fn=None, **_kw):
+        if fn is None:
+            return lambda f: f
+        return fn
+    def task(fn=None, **_kw):
+        if fn is None:
+            return lambda f: f
+        return fn
+    def get_run_logger():  # pragma: no cover
+        import logging
+        return logging.getLogger("s6_recompute_flow")
+
+
+REPO_ROOT    = Path(__file__).resolve().parents[1]
+RECOMPUTE_PY = REPO_ROOT / "prod" / "scripts" / "recompute_s6_coefficients.py"
+TABLE_YML    = REPO_ROOT / "prod" / "configs" / "green_s6_table.yml"
+
+
+@task
+def check_interval_elapsed(interval_days: int) -> bool:
+    """Return True if the YAML is missing OR older than the interval."""
+    if not TABLE_YML.exists():
+        return True
+    try:
+        import yaml
+        doc = yaml.safe_load(TABLE_YML.read_text()) or {}
+        ts_str = (doc.get("meta") or {}).get("generated_at", "")
+        if not ts_str:
+            return True
+        ts = datetime.fromisoformat(ts_str.rstrip("Z"))
+        return datetime.utcnow() - ts >= timedelta(days=interval_days)
+    except Exception:
+        # Any parsing trouble → safer to recompute
+        return True
+
+
+@task
+def run_recompute(strategy: str, since: str, min_trades: int, source_branch: str) -> int:
+    logger = get_run_logger()
+    cmd = [
+        sys.executable, str(RECOMPUTE_PY),
+        "--strategy", strategy,
+        "--since",    since,
+        "--min-trades-per-bucket", str(min_trades),
+        "--source-branch", source_branch,
+    ]
+    logger.info(f"[s6_recompute_flow] exec: {' '.join(cmd)}")
+    rc = subprocess.call(cmd, cwd=str(REPO_ROOT))
+    logger.info(f"[s6_recompute_flow] exit code: {rc}")
+    return rc
+
+
+@flow(name="s6-recompute")
+def s6_recompute_flow(
+    strategy: str = "blue",
+    since: str = "2026-01-01",
+    min_trades: int = 20,
+    source_branch: str = "exp/green-s6-esof-aem-shadow-2026-04-21",
+):
+    logger = get_run_logger()
+
+    if os.environ.get("S6_RECOMPUTE_DISABLED") == "1":
+        logger.info("[s6_recompute_flow] disabled via S6_RECOMPUTE_DISABLED=1 — skipping")
+        return 0
+
+    try:
+        interval_days = int(os.environ.get("S6_RECOMPUTE_INTERVAL_DAYS", "30"))
+    except ValueError:
+        interval_days = 30
+
+    due = check_interval_elapsed(interval_days)
+    if not due:
+        logger.info(f"[s6_recompute_flow] interval not elapsed ({interval_days}d) — skipping")
+        return 0
+
+    return run_recompute(strategy, since, min_trades, source_branch)
+
+
+if __name__ == "__main__":
+    sys.exit(int(s6_recompute_flow() or 0))