Extract attach-bsdl into core; add it to the wx GUI.

Second editing op into the wx frontend. Extract the logic (parse the .bsd,
apply it to the part, record bsdl_path) into core/app/edit.hpp::attach_bsdl
(Part*, path) -> {ok, error, entity, bound, unbound, ports_total}, failing
without mutation when the file can't be parsed.

The TUI `attach-bsdl` command now renders that result (output unchanged); the
wx GUI gains an Edit ▸ Attach BSDL… menu reusing PickPart() + a .bsd file
dialog. Prune the now-dead bsdl_model include from commands.cpp.

tests/test_edit.cpp: parse failure leaves the part untouched; null part. The
success path is covered by a batch run (entity + bound/total ports). 381 core
assertions green; tui + wx build clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/frontends/wx/wx_frame.hpp

@@ -23,6 +23,7 @@ private:
     void OnSave(wxCommandEvent &);
     void OnExport(wxCommandEvent &);
     void OnSetConnectorType(wxCommandEvent &);
+    void OnAttachBsdl(wxCommandEvent &);
     void OnVerify(wxCommandEvent &);
     void OnQuit(wxCommandEvent &);
     void OnAbout(wxCommandEvent &);