- replace instant drag-on-press with 500ms long-press timer
- cancel long-press on early release or movement past 10px threshold
- preserve double-click for mouse users (backward compatible)
- resize edge detection still instant (no long-press)
- cancel long-press on mouse_exit and grid rebuild
- fix: ConfigFile reserved word 'default' removed from config
- plugin_manager: scans res://plugins/*/plugin.cfg, loads tile definitions
- plugin_tile: new base class for plugin tiles, extends ModuleBase
- layout_manager: save/restore tile grid positions per named layout
- migrate existing cpu/memory/testing tiles into system_monitor plugin
- add module_resized signal to DashboardGrid for auto-save
- dashboard reads from PluginManager + LayoutManager instead of hardcoded paths
- project.godot registers PluginManager and LayoutManager autoloads
- AGENTS.md updated with new structure and conventions
