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/data/db.py

@@ -89,6 +89,23 @@ class Database:
             )
             return {r["family_key"] for r in rows if r["family_key"]}
 
+    async def get_open_position_details(self) -> list[dict]:
+        """Return one row per open position with family_key and direction.
+
+        Used at startup to detect positions that share a family_key (same
+        underlying event), which indicates a contradictory paper trade entered
+        before the general-election family fix was deployed.
+        """
+        async with self._pool.acquire() as conn:
+            rows = await conn.fetch("""
+                SELECT DISTINCT ON (market_id)
+                    market_id, question, direction, edge_net, family_key, timestamp
+                FROM trades
+                WHERE paper = TRUE
+                ORDER BY market_id, timestamp DESC
+            """)
+            return [dict(r) for r in rows]
+
     async def get_recent_trades(self, limit: int = 100) -> list[dict]:
         async with self._pool.acquire() as conn:
             rows = await conn.fetch(