fix(critical): complementary market family grouping + Manifold inversion guard

FASE 1 — market_family_key() general election fix
General elections now group by office, not by party, so complementary
markets ("Republicans win Ohio governor" / "Democrats win Ohio governor")
share the same family key (ohio-gubernatorial-2026).  The second market
is blocked by the occupied_families check rather than traded as independent.

Primaries still keep the party (texas-republican-2026) because each party
runs its own separate primary race.

FASE 2 — Manifold party inversion guard
_detect_party() identifies the winning side in both the Polymarket question
and the matched Manifold title.  If they are confirmed opposites (republican
vs democrat), the probability is inverted (1 - prob) before use.

Full audit log per query:
  poly_question / manifold_title / manifold_url / match_score /
  prob_raw / inverted / prob_final

Root cause of Ohio Manifold:0.95 on both sides: both queries matched the
same Manifold market ("Republicans win Ohio governor" prob=0.95).  For the
"Democrats win" query the inversion now produces prob_final=0.05 instead of
blindly applying 0.95 to the wrong direction.

FASE 4 — startup contradiction scan
get_open_position_details() added to db.py.  main.py checks all open
positions at startup, warns on any family with >1 position, and recommends
keeping the one with the highest edge_net.  No auto-close.

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

bot/main.py

@@ -202,6 +202,30 @@ async def main() -> None:
     if PAPER_MODE:
         await executor.initialize()
 
+    # Contradiction scan: warn if any two open positions share a family_key.
+    # This can happen when the family logic was less strict on a prior deploy.
+    # Bot does NOT auto-close — operator decides which position to keep.
+    positions = await db.get_open_position_details()
+    family_map: dict[str, list[dict]] = {}
+    for pos in positions:
+        fk = pos.get("family_key") or ""
+        if fk:
+            family_map.setdefault(fk, []).append(pos)
+    for fk, members in family_map.items():
+        if len(members) > 1:
+            best = max(members, key=lambda p: p.get("edge_net") or 0.0)
+            log.warning(
+                "CONTRADICTION family=%s has %d open positions — recommend keeping market_id=%s (edge_net=%.3f):",
+                fk, len(members), best["market_id"], best.get("edge_net") or 0.0,
+            )
+            for m in members:
+                marker = "KEEP" if m["market_id"] == best["market_id"] else "REVIEW"
+                log.warning(
+                    "  [%s] %s | dir=%s | edge_net=%.3f | %s",
+                    marker, m["market_id"], m["direction"],
+                    m.get("edge_net") or 0.0, m["question"][:60],
+                )
+
     try:
         await run_trading_loop(poly, external, strategy, risk, executor, metrics, db)
     finally: