Improve file loading robustness and drag-and-drop handling

- Add error handling for UTF-8 decoding to gracefully handle invalid bytes
- Refactor DnD target handling with explicit target list and proper context completion
- Remove completed TODO item for file open event emission
- Clean up memory by deleting file contents after decoding

TODO.md

@@ -4,7 +4,6 @@ ___
 1. Add TreeSitter
 1. Add Collapsable code blocks
 1. Add Terminal plugin
-1. Add event to emit on file open so plugins could try to open
 1. Add Plugin to <Shift\><Ctrl\>| and <Ctrl\>| to split views up, down, left, right
 1. Add <Ctrl\>i to **lsp_manager** to list who implements xyz