/usr/include/geany/ is in geany-common 1.23.1+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/geany/build.h
/usr/include/geany/document.h
/usr/include/geany/editor.h
/usr/include/geany/encodings.h
/usr/include/geany/filetypes.h
/usr/include/geany/geany.h
/usr/include/geany/geanyfunctions.h
/usr/include/geany/geanyplugin.h
/usr/include/geany/highlighting.h
/usr/include/geany/keybindings.h
/usr/include/geany/msgwindow.h
/usr/include/geany/plugindata.h
/usr/include/geany/prefs.h
/usr/include/geany/project.h
/usr/include/geany/scintilla/
/usr/include/geany/scintilla/SciLexer.h
/usr/include/geany/scintilla/Scintilla.h
/usr/include/geany/scintilla/Scintilla.iface
/usr/include/geany/scintilla/ScintillaWidget.h
/usr/include/geany/search.h
/usr/include/geany/stash.h
/usr/include/geany/support.h
/usr/include/geany/tagmanager/
/usr/include/geany/tagmanager/tm_file_entry.h
/usr/include/geany/tagmanager/tm_project.h
/usr/include/geany/tagmanager/tm_source_file.h
/usr/include/geany/tagmanager/tm_symbol.h
/usr/include/geany/tagmanager/tm_tag.h
/usr/include/geany/tagmanager/tm_tagmanager.h
/usr/include/geany/tagmanager/tm_work_object.h
/usr/include/geany/tagmanager/tm_workspace.h
/usr/include/geany/templates.h
/usr/include/geany/toolbar.h
/usr/include/geany/ui_utils.h
/usr/include/geany/utils.h