Fix script links after Explorer renames and moves

[JamieW105]

Renaming an attached script in Explorer previously left its registry path pointing to the old filename, so Play could no longer find the source. Explorer now updates the script registry while keeping the attachment ID, language, and properties intact. File moves and folder renames/moves update all affected script paths. Failed registry saves roll back the file and metadata move. Invalid script destinations and registry collisions are rejected.

Companion documentation: Rustic-Game-Engine/docs#43

Validation:

• cargo test -p rustic-editor explorer_tests --no-fail-fast: 20 passed, including script identity, nested relocations, failed-save rollback, and invalid destinations.
• cargo fmt --all --check: passed.
• cargo clippy --locked -p rustic-editor --all-targets -- -D warnings: passed.
• Documentation lint, production build, TypeScript, and npm audit: passed.
• Windows installer build and packaged Setup tests: passed; a fresh dist/RusticGameEngine-Setup-*.exe was uploaded as RusticGameEngine-Windows-Installer: https://github.com/Rustic-Game-Engine/engine/actions/runs/38538271564.
• Full Linux CI (workspace lint, tests, rendered viewport verification, target checks, and application smoke tests): passed.