Dimensium

### Added
- Replace mode: toggle via a configurable keybind (default: unbound) to replace existing blocks on right-click; targeted block is highlighted in red while mode is active

### Changed
- Paste and selection fill/delete: use bulk chunk writes and deferred lighting instead of per-block world updates
- Selection window: "Move Selection" now moves the selection itself (not the blocks) via interactive gizmos — center gizmo for all selections, plus min/max corner gizmos for cuboid (AABB) selections; confirm with Enter, cancel with Escape or RMB

### Fixed
- All popups: fix popup flashing closed immediately after save-quitting and reopening a world
- All tools: fix placed leaves decaying when not adjacent to a log
- Box select tool: clicking empty space no longer accidentally confirms the bounding box

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**Full Changelog**: https://github.com/thehighcruw/Dimensium/compare/v0.1.1...v0.1.2