feat(state): dvol_history multi-asset (ETH+BTC) + backfill ETH legacy rows

Migration 0006 promuove dvol_history da PK=(timestamp) mono-ETH a
PK=(timestamp, asset), rinomina eth_spot -> spot, e backfilla con
asset='ETH' le righe storiche. market_snapshot_cycle ora scrive sia
per ETH che per BTC; monitor_cycle resta ETH-only via WHERE asset='ETH'
nella lookup di return_4h.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/test_market_snapshot_cycle.py

@@ -38,7 +38,9 @@ def _ctx(tmp_path: Path) -> MagicMock:
 
     # Default: every feed succeeds with sane mock values.
     ctx.deribit = MagicMock()
-    ctx.deribit.spot_perp_price = AsyncMock(return_value=Decimal("3000"))
+    ctx.deribit.spot_perp_price = AsyncMock(
+        side_effect=lambda asset: Decimal("65000") if asset == "BTC" else Decimal("3000")
+    )
     ctx.deribit.latest_dvol = AsyncMock(return_value=Decimal("55"))
     ctx.deribit.realized_vol = AsyncMock(
         return_value={
@@ -181,31 +183,35 @@ def _read_dvol_history(ctx: MagicMock) -> list[dict]:
 
 
 @pytest.mark.asyncio
-async def test_eth_snapshot_mirrors_into_dvol_history(tmp_path: Path) -> None:
+async def test_snapshot_mirrors_each_asset_into_dvol_history(tmp_path: Path) -> None:
     ctx = _ctx(tmp_path)
     await collect_market_snapshot(ctx, assets=("ETH", "BTC"), now=_now())
     rows = _read_dvol_history(ctx)
-    assert len(rows) == 1
-    assert Decimal(str(rows[0]["dvol"])) == Decimal("55")
-    assert Decimal(str(rows[0]["eth_spot"])) == Decimal("3000")
+    by_asset = {r["asset"]: r for r in rows}
+    assert set(by_asset) == {"ETH", "BTC"}
+    assert Decimal(str(by_asset["ETH"]["spot"])) == Decimal("3000")
+    assert Decimal(str(by_asset["BTC"]["spot"])) == Decimal("65000")
 
 
 @pytest.mark.asyncio
-async def test_btc_only_snapshot_does_not_touch_dvol_history(
+async def test_btc_only_snapshot_mirrors_into_dvol_history(
     tmp_path: Path,
 ) -> None:
     ctx = _ctx(tmp_path)
     await collect_market_snapshot(ctx, assets=("BTC",), now=_now())
-    assert _read_dvol_history(ctx) == []
+    rows = _read_dvol_history(ctx)
+    assert len(rows) == 1
+    assert rows[0]["asset"] == "BTC"
+    assert Decimal(str(rows[0]["spot"])) == Decimal("65000")
 
 
 @pytest.mark.asyncio
-async def test_eth_snapshot_skips_dvol_history_when_dvol_missing(
+async def test_snapshot_skips_dvol_history_when_dvol_missing(
     tmp_path: Path,
 ) -> None:
     ctx = _ctx(tmp_path)
     ctx.deribit.latest_dvol = AsyncMock(side_effect=RuntimeError("no dvol"))
     await collect_market_snapshot(ctx, assets=("ETH",), now=_now())
     # market_snapshots row still persisted, but dvol_history must stay empty
-    # because its schema enforces NOT NULL on dvol/eth_spot.
+    # because its schema enforces NOT NULL on dvol/spot.
     assert _read_dvol_history(ctx) == []

tests/unit/test_state_repository.py

@@ -277,15 +277,46 @@ def test_record_dvol_snapshot_replaces_on_duplicate_timestamp(
     ts = datetime(2026, 4, 27, 14, 0, tzinfo=UTC)
     with transaction(conn):
         repo.record_dvol_snapshot(
-            conn, DvolSnapshot(timestamp=ts, dvol=Decimal("50"), eth_spot=Decimal("3000"))
+            conn,
+            DvolSnapshot(
+                timestamp=ts, asset="ETH", dvol=Decimal("50"), spot=Decimal("3000")
+            ),
         )
         repo.record_dvol_snapshot(
-            conn, DvolSnapshot(timestamp=ts, dvol=Decimal("55"), eth_spot=Decimal("3050"))
+            conn,
+            DvolSnapshot(
+                timestamp=ts, asset="ETH", dvol=Decimal("55"), spot=Decimal("3050")
+            ),
         )
     rows = conn.execute("SELECT COUNT(*) FROM dvol_history").fetchone()
     assert rows[0] == 1
 
 
+def test_record_dvol_snapshot_keeps_assets_distinct_on_same_timestamp(
+    conn: sqlite3.Connection, repo: Repository
+) -> None:
+    ts = datetime(2026, 4, 27, 14, 0, tzinfo=UTC)
+    with transaction(conn):
+        repo.record_dvol_snapshot(
+            conn,
+            DvolSnapshot(
+                timestamp=ts, asset="ETH", dvol=Decimal("50"), spot=Decimal("3000")
+            ),
+        )
+        repo.record_dvol_snapshot(
+            conn,
+            DvolSnapshot(
+                timestamp=ts, asset="BTC", dvol=Decimal("45"), spot=Decimal("65000")
+            ),
+        )
+    rows = conn.execute(
+        "SELECT asset, dvol, spot FROM dvol_history ORDER BY asset"
+    ).fetchall()
+    assert [r["asset"] for r in rows] == ["BTC", "ETH"]
+    assert Decimal(str(rows[0]["spot"])) == Decimal("65000")
+    assert Decimal(str(rows[1]["spot"])) == Decimal("3000")
+
+
 def test_manual_action_enqueue_consume_cycle(
     conn: sqlite3.Connection, repo: Repository
 ) -> None: