feat: initial scaffold kanban_cpp v0.1.0

C++ ImGui kanban for steering LLM agents. Six panels (Board, Calendar,
Dashboard, Agent runs, Worktrees, DoD inspector) wired to registry
functions http_request, kpi_card, sparkline, agent_runs_timeline,
dod_evidence_panel. Backend Go on :8403 (independent operations.db from
kanban_web).

CMakeLists.txt

@@ -0,0 +1,24 @@
+add_imgui_app(kanban_cpp
+    main.cpp
+    data.cpp
+    panel_board.cpp
+    panel_calendar.cpp
+    panel_dashboard.cpp
+    panel_agent_runs.cpp
+    panel_worktrees.cpp
+    panel_dod.cpp
+    # Registry functions consumed (see app.md::uses_functions)
+    ${CMAKE_SOURCE_DIR}/functions/core/http_request.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/kpi_card.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/sparkline.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/agent_runs_timeline.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/agent_runs_timeline_helpers.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/dod_evidence_panel.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/dod_evidence_panel_helpers.cpp
+)
+target_include_directories(kanban_cpp PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+
+if(WIN32)
+    target_link_libraries(kanban_cpp PRIVATE ws2_32)
+    set_target_properties(kanban_cpp PROPERTIES WIN32_EXECUTABLE TRUE)
+endif()