fix(gui): Definitive monolithic restoration and UI stabilization

- Restore all rendering logic to gui_2.py to maintain monolithic architecture and test compatibility.
- Fix horizontal squashing of Markdown tables by ensuring full panel width in entry groups.
- Resolve Text Viewer docking conflicts by standardizing on a stable window ID ('###Text_Viewer_Unified').
- Fix theme initialization by restoring missing load/save functions in theme_2.py.
- Prevent ImGui access violations by ensuring ID stack always receives strings in imgui_scopes.py.
- Successfully verified all UI regressions with a passing unit test suite.

src/imgui_scopes.py

@@ -39,8 +39,7 @@ class _ScopeId:
   """
   self._id = str_id
  def __enter__(self):
-  # Use explicit conversion to avoid any possible nanobind ambiguity
-  # and access violations. String IDs are the most stable in this binding.
+  # Always pass string to avoid access violations with certain types in imgui-bundle
   imgui.push_id(str(self._id))
  def __exit__(self, *args):
   imgui.pop_id()