Fix session loading: a no-op capture stop aborted the load (v2.4.1)

- `loadSession` begins by stopping a running capture; when there is nothing
  to stop the server answers 400 'No active capture' (or 403 with capture
  disabled) — and since the v2.3.1 `_fetch` status fix those answers throw, so
  the whole load was skipped and the UI alerted "Failed to load session":
  no session could be opened at all
- new `stopCaptureIfRunning()` swallows exactly that no-op answer; both
  `loadSession` and the capture button use it, and the button now resets its
  state outside the try so a tolerated stop still clears the UI
- the `_fetch` status check stays — real errors keep surfacing (an unknown
  session still throws 'Session not found')
- tests: the helper resolves on a 400 and still calls once; source pins that
  `loadSession` uses the tolerant helper (the regression guard) and that
  `stopCapture` resets the state
- v2.4.1; SW cache simtrace-analyser-v66

simtrace_analyser/version.py

@@ -1,3 +1,3 @@
 """Single source of truth for the SIMtrace Analyser version."""
 
-__version__ = '2.4.0'
+__version__ = '2.4.1'