ibkr: emit ibkr_cash_balance{currency, account} per CashReport row

Each daily run now pushes one Pushgateway metric per currency row from
the Flex Activity Query's CashReport section (typically BASE_SUMMARY
aggregate + one row per held currency). Makes dormant-account balance
checks trivial and adds a Grafana surface for cash drift alerting.

Requires the Activity Flex Query in IBKR Client Portal to have the
CashReport section enabled.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

broker_sync/cli.py

@@ -310,6 +310,16 @@ def ibkr(
                         float(drift),
                     )
                 )
+            # Cash balances (one row per currency from CashReport, plus a
+            # BASE_SUMMARY row consolidated in account base currency).
+            for currency, ending_cash in provider.cash_balances():
+                drift_metrics.append(
+                    (
+                        "ibkr_cash_balance",
+                        {"currency": currency, "account": "ibkr-uk"},
+                        float(ending_cash),
+                    )
+                )
             drift_metrics.append(
                 ("ibkr_sync_last_success_timestamp_seconds", {}, float(time.time()))
             )

broker_sync/providers/ibkr.py

@@ -257,3 +257,20 @@ class IBKRProvider:
             )
             out.append((symbol, Decimal(str(pos.position))))
         return out
+
+    def cash_balances(self) -> list[tuple[str, Decimal]]:
+        """Return ``[(currency, ending_cash), ...]`` from the CashReport.
+
+        Includes the ``BASE_SUMMARY`` aggregate row (account base currency
+        consolidated) plus any per-currency rows. Empty list if no
+        CashReport section in the Flex query or before first ``fetch()``.
+        """
+        if self._last_response is None:
+            return []
+        stmt = self._last_response.FlexStatements[0]
+        out: list[tuple[str, Decimal]] = []
+        for row in stmt.CashReport or []:
+            if row.endingCash is None or row.currency is None:
+                continue
+            out.append((str(row.currency), Decimal(str(row.endingCash))))
+        return out

tests/fixtures/ibkr/sample_flex.xml

@@ -16,6 +16,10 @@
         <OpenPosition symbol="VUAG" position="8" markPrice="108.20" currency="GBP" assetCategory="STK"/>
         <OpenPosition symbol="AAPL" position="5" markPrice="181.00" currency="USD" assetCategory="STK"/>
       </OpenPositions>
+      <CashReport>
+        <CashReportCurrency accountId="U12345678" currency="BASE_SUMMARY" levelOfDetail="BaseCurrency" startingCash="1.23" endingCash="1.23" endingSettledCash="1.23"/>
+        <CashReportCurrency accountId="U12345678" currency="USD" levelOfDetail="Currency" startingCash="1.23" endingCash="1.23" endingSettledCash="1.23"/>
+      </CashReport>
     </FlexStatement>
   </FlexStatements>
 </FlexQueryResponse>

tests/providers/test_ibkr.py

@@ -194,3 +194,31 @@ async def test_ibkr_provider_open_positions_after_fetch(
     positions = provider.open_positions()
     # VUAG → VUAG.L (LSE inferred from GBP); AAPL unchanged (USD)
     assert dict(positions) == {"VUAG.L": Decimal("8"), "AAPL": Decimal("5")}
+
+
+async def test_ibkr_provider_cash_balances_after_fetch(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """cash_balances() returns (currency, ending_cash) tuples from CashReport."""
+    from ibflex import client as ib_client
+
+    with open("tests/fixtures/ibkr/sample_flex.xml", "rb") as f:
+        xml_bytes = f.read()
+    monkeypatch.setattr(ib_client, "download", lambda *a, **kw: xml_bytes)
+
+    provider = IBKRProvider(
+        token="t",
+        query_id="q",
+        upstream_account_id="U12345678",
+    )
+    [a async for a in provider.fetch()]
+
+    balances = provider.cash_balances()
+    # Fixture has BASE_SUMMARY + USD rows, both 1.23
+    assert dict(balances) == {"BASE_SUMMARY": Decimal("1.23"), "USD": Decimal("1.23")}
+
+
+def test_ibkr_provider_cash_balances_before_fetch_returns_empty() -> None:
+    """No CashReport data before fetch()."""
+    provider = IBKRProvider(token="t", query_id="q", upstream_account_id="U12345678")
+    assert provider.cash_balances() == []