Remap non-std IB exchange values

Add exchange name translation in `.ib.venues.has_holiday()` to handle
non-standard exchange codes when looking up holiday gaps..

Deats,
- add an ad-hoc lookup dict to remap an IB `Contract.primaryExchange` val
  which doesn't exist in the `exchange_calendars`'s alias set.
- use `.get()` with fallback to map `exch` to new `std_exch` and pass
  that to `xcals.get_calendar()`.
- add the case i just caught, `'ARCA'` -> `'ARCX'` to the table when i loaded
  the `gld.arca.ib` market..

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/brokers/ib/venues.py

@@ -83,7 +83,14 @@ def has_holiday(
     '''
     tz: str = con_deats.timeZoneId
     exch: str = con_deats.contract.primaryExchange
-    cal: ExchangeCalendar = xcals.get_calendar(exch)
+
+    # XXX, ad-hoc handle any IB exchange which are non-std
+    # via lookup table..
+    std_exch: dict = {
+        'ARCA': 'ARCX',
+    }.get(exch, exch)
+
+    cal: ExchangeCalendar = xcals.get_calendar(std_exch)
     end: datetime = period.end
     # _start: datetime = period.start
     # ?TODO, can rm ya?