Flaky test: ServerErrorAckTerminalTest.testServerErrorAckIsTerminalAndDoesNotBurnReconnectBudget #110

Failed on CI (Azure build 279451, Coverage Report job, PR #109):

LineSenderServerException: server rejected batch: PARSE_ERROR (status=0x5) fsn=[0,0] seq=0 - test: parse error

Cause: a race in the test. The fake server answers every frame with a terminal PARSE_ERROR. flush() publishes the batch and then calls cursorSendLoop.checkError() (QwpWebSocketSender.java:2242). On loopback the error ACK can be received and latched before that check runs (the CI log shows publish, latch and close within 1 ms), so the first flush() throws. The test calls it outside any try/catch (ServerErrorAckTerminalTest.java:81) and expects the error only from the second flush.

Fix: tolerate a LineSenderException from the first flush(). The terminal is sticky, so the second flush still throws and the existing assertions hold.