fix return-value/deprecated API bugs, accumulation lock leaks, code cleanup

- raise instead of silent None for unsupported operands and empty negation
- validate before acquiring lock in Accumulation operators (no RLock leak)
- Accumulation._copy_provenance helper, ADC_Result._copy_metadata for all result paths
- shared _sandbox_stdout_redirect contextmanager for sandboxed scripts
- TemperatureMonitor dead code removal (gtk helper, traceback, unused properties)
- new unit tests incl. lock-freedom regression test
- gitignore sphinx generated doc/_autosummary/ and doc/damaris/

doc/api_reference.rst

@@ -26,6 +26,7 @@ The data module contains result types, data handling, and signal processing clas
 
    damaris.data.ADC_Result
    damaris.data.Accumulation
+   damaris.data.Config_Result
    damaris.data.DamarisFFT
    damaris.data.DataPool
    damaris.data.Drawable
@@ -71,6 +72,20 @@ The GUI module contains the graphical interface, backend driver, and experiment/
    damaris.gui.TemperatureMonitor
    damaris.gui.logging_utils
 
+A short usage example for the font helper of the GUI module (the non-deprecated
+replacement for the removed ``Widget.modify_font()``):
+
+.. code-block:: python
+
+   from damaris.gui.DamarisGUI import apply_font_css
+
+   apply_font_css(textview, "Monospace 10")   # pango style font description
+   apply_font_css(label, "sans bold 16")
+
+The font string is converted into a CSS rule (``font-family``/``font-size``/
+``font-weight``) which is applied to the widget's style context with a
+``Gtk.CssProvider``.
+
 
 Tools Module
 ============