fix(gui): Final Phase 7 stabilization and polish

- Resolve ImportError by correctly prefixing 'src' in modular renderers.
- Fix ImGui access violation by ensuring push_id always receives string IDs.
- Restore visible role-based background tints using layered rendering (channels).
- Definitively fix horizontal Markdown table widths by forcing group expansion.
- Centralize color management in theme_2.py and ui_shared.py.
- Standardize Files & Media inventory layout and remove legacy controls.
- Update test mocks to support modular UI and theme-driven styling.

src/imgui_scopes.py

@@ -39,7 +39,9 @@ class _ScopeId:
   """
   self._id = str_id
  def __enter__(self):
-  imgui.push_id(self._id)
+  # Use explicit conversion to avoid any possible nanobind ambiguity
+  # and access violations. String IDs are the most stable in this binding.
+  imgui.push_id(str(self._id))
  def __exit__(self, *args):
   imgui.pop_id()
   return False