Kate's project plugin already opens folders and shows a file tree, and we
now build on it via KateProjectBridge, so the parallel Ollie-side model
was redundant. Remove the Alt+O 'Open Folder as Project' action, the
sticky m_projectRoot + its $XDG_CONFIG_HOME/olliepalette/project
persistence (load/save), 'Close Project', and the ollie:project:* palette
entries/handlers. currentProjectRoot() is now two-tier: bridge baseDir
-> VCS discovery. Frees Alt+O. 12 ctest suites still pass.