Complete RmlUi conversion - remove all Chili framework code

This commit completes the conversion from Chili framework to RmlUi by:

1. Removed all legacy Chili-based view code (104+ files)
   - Deleted scen_edit/view/actions/, fields/, floating/, map/, object/, trigger/
   - Deleted all old dialog implementations
   - Deleted Chili widget (LuaUI/widgets/api_sb_chili.lua)

2. Restructured view directory
   - Moved view_rmlui/* to view/
   - Removed "rmlui_" prefix from all filenames
   - Cleaned up duplicate view_rmlui directory

3. Renamed classes for clarity
   - RmlUiManager -> UIManager (SB.rmlui -> SB.ui)
   - RmlUiDialog -> Dialog
   - RmlUiFileDialog -> FileDialog
   - RmlUiNewProjectDialog -> NewProjectDialog
   - RmlUiSaveProjectDialog -> SaveProjectDialog
   - RmlUiOpenProjectDialog -> OpenProjectDialog
   - ViewRmlUi -> View

4. Updated all references throughout codebase
   - Changed all SB.rmlui to SB.ui
   - Changed all view_rmlui paths to view
   - Updated imports in init.lua, view.lua, all dialogs
   - Updated widget (api_sb_ui.lua)
   - Updated test harness and documentation

5. Removed Chili exports
   - Cleaned up scen_edit/exports.lua
   - Removed all Chili framework references

The UI now uses proper declarative RmlUi pattern:
- RML files for structure (view/rml/)
- RCSS files for styling (view/rcss/)
- Lua files for logic only

All dialog components converted and functional.

Author: claude