refactor(gui): move the Hesiod node proxy out of the model (step 3)

[barrulus]

BaseNode currently supplies GNodeGUI’s proxy interface, pulling Qt into model headers and exposing GUI port directions to model code. This moves that interface into HesiodNodeProxy in the GUI layer while preserving node/port IDs, captions, comments, tooltips and data access.

Step 3 of #751; depends on #771. This branch includes step 2 until that PR merges. Review the step 3 change separately in commit 3a649cbb.

• Give the widget ownership of the proxy through QObject parenting, with a weak reference to the graph-owned model and safe empty values after model expiry.
• Use GNode’s existing accessors and port directions in model code, port selection, previews and CLI checks. Reuse GNodeGUI’s default port-ID handling; remove the old model proxy wrappers.
• Exercise the actual adapter in the editor integration suite and compile BaseNode, GraphNode and PortCatalog headers without Qt or GNodeGUI include paths.

This removes the GUI dependency from these model headers. Existing model implementations still use Qt and application services; remaining settings/update paths are a follow-up step.

Validation on upstream dev (f62c18c5): application build and model-header compilation passed; all 29 Qt checks passed.

cmake --build build --target hesiod test_graph_editor -j 12
ctest --test-dir build -R '^graph_editor$' --output-on-failure