Mod+Shift+D is Move Column Right in Dank Material Shell's niri binds (dms/binds.kdl), so the shipped example competed with it silently. The toggle moves to Mod+Shift+M, which is free in niri's stock binds and in DMS's binds. The start and stop examples move off Mod+Shift+E, which is stock niri's quit, to Mod+Shift+S and Mod+Shift+X. niri validate rejects a key bound twice in one binds block but not across blocks, so validation cannot show a conflict. The docs now give a grep over the config tree and niri's embedded stock binds for checking a key before binding it. The overlay pointer is corrected to Mod+Shift+Slash. A test pins the doc and the include to one toggle key that is not Mod+Shift+D. Fixes #45