Handle `str`-errors in `.ib.broker` trade events

Add `isinstance()` dispatch for the `'error'` event case in
`deliver_trade_events()` to handle `ib_async` sometimes emitting plain
`str` error items instead of the previously expected `dict`.

Deats,
- add `isinstance(err, dict)` branch for the standard case with
  `error_code`, `reason`, and `reqid` fields.
- add `isinstance(err, str)` branch to parse error strings of the
  form `'[code 104] connection failed'` into `code` and `reason`.
- set `reqid: str = '<unknown>'` for string-form errors since
  there's no request ID available.
- update `err` type annot to `dict|str`.

(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/broker.py

@@ -1291,13 +1291,23 @@ async def deliver_trade_events(
             case 'error':
                 # NOTE: see impl deats in
                 # `Client.inline_errors()::push_err()`
-                err: dict = item
+                err: dict|str = item
 
-                # never relay errors for non-broker related issues
+                # std case, never relay errors for non-order-control
+                # related issues.
                 # https://interactivebrokers.github.io/tws-api/message_codes.html
-                code: int = err['error_code']
-                reason: str = err['reason']
-                reqid: str = str(err['reqid'])
+                if isinstance(err, dict):
+                    code: int = err['error_code']
+                    reason: str = err['reason']
+                    reqid: str = str(err['reqid'])
+
+                # XXX, sometimes you'll get just a `str` of the form,
+                # '[code 104] connection failed' or something..
+                elif isinstance(err, str):
+                    code_part, _, reason = err.rpartition(']')
+                    if code_part:
+                        _, _, code = code_part.partition('[code')
+                    reqid: str = '<unknown>'
 
                 # "Warning:" msg codes,
                 # https://interactivebrokers.github.io/tws-api/message_codes.html#warning_codes