chore: scaffold skill_tree (issue 0109)

Initial scaffold via init_cpp_app_bash_pipelines:
- main.cpp con Tree + Inspector panels (placeholders)
- app.md con trio icon (tree-structure + #c026d3) + e2e_checks
- CMakeLists.txt via add_imgui_app
- appicon.ico generado con generate_app_icon_py_infra

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -0,0 +1,14 @@
+add_imgui_app(skill_tree
+    main.cpp
+)
+target_include_directories(skill_tree PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+
+# fn_table_viz: provides data_table::render(), viz_render, TQL engine, Lua, LLM.
+# Guard keeps the app compilable in builds where vendor/lua is absent.
+if(TARGET fn_table_viz)
+    target_link_libraries(skill_tree PRIVATE fn_table_viz)
+endif()
+
+if(WIN32)
+    set_target_properties(skill_tree PROPERTIES WIN32_EXECUTABLE TRUE)
+endif()