feat(primitives_gallery): demo de sql_workbench contra registry.db readonly

Demo nuevo en demos_sql.cpp: abre registry.db en SQLITE_OPEN_READONLY
(resolviendo via FN_REGISTRY_ROOT o cwd ascendente), monta
fn::SqlWorkbenchState con readonly=true y query inicial sobre la tabla
functions. Wire-up: entry en k_demos[] tras process_runner; declaracion
en demos.h; sources sql_workbench.cpp + demos_sql.cpp + link
SQLite::SQLite3 en CMakeLists.txt.

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

cpp/apps/primitives_gallery/CMakeLists.txt

@@ -8,10 +8,13 @@ add_imgui_app(primitives_gallery
     demos_text_editor.cpp
     demos_gl_texture.cpp
     demos_extras.cpp
+    demos_sql.cpp
     # text_editor + file_watcher (issue 0025)
     ${CMAKE_SOURCE_DIR}/functions/core/text_editor.cpp
     ${CMAKE_SOURCE_DIR}/functions/core/file_watcher.cpp
     ${CMAKE_SOURCE_DIR}/vendor/imgui_text_edit/TextEditor.cpp
+    # sql_workbench (issue 0032)
+    ${CMAKE_SOURCE_DIR}/functions/core/sql_workbench.cpp
     # Core primitives demoed (tokens vive en fn_framework)
     ${CMAKE_SOURCE_DIR}/functions/core/fullscreen_window.cpp
     ${CMAKE_SOURCE_DIR}/functions/core/page_header.cpp
@@ -61,6 +64,10 @@ target_include_directories(primitives_gallery PRIVATE
     ${CMAKE_SOURCE_DIR}/vendor/stb
 )
 
+# SQLite (sql_workbench) — alias provisto por cpp/CMakeLists.txt:
+# system on Linux, vendored amalgamation on Windows cross-compile.
+target_link_libraries(primitives_gallery PRIVATE SQLite::SQLite3)
+
 if(WIN32)
     target_link_libraries(primitives_gallery PRIVATE opengl32)
 endif()