fix: race condition in IdeStreamingSink

[thomhurst]

Description

IdeStreamingSink.cs (Lines 147-152)

Double-check locking pattern without proper synchronization:

if (state.IsCompleted || testContext.Result is not null) { state.TryMarkCompleted(); return; }
// ... Send update
if (state.IsCompleted || testContext.Result is not null) { state.TryMarkCompleted(); return; }

Between the first check and sending the update, another thread could mark the test as completed, resulting in state updates being sent after test completion. This could cause IDE test explorers to receive updates after seeing the final state, causing UI glitches.

Timer Leak (Lines 80-85)

Timer is created with new Timer() but if an exception occurs during CreateStreamingState, the timer could leak. Dispose() is only called in CleanupTest().

Suggested Fix

• Use a single atomic check: if (!state.TryMarkCompleted()) return;
• Wrap state creation in try-catch and always dispose the timer on failure