Add --git-since option to rojo serve

- Add new GitFilter struct for tracking files changed since a Git reference
- Only sync changed (added/deleted/modified) files to Roblox Studio
- Files remain acknowledged once synced, even if content is reverted
- Add enhanced logging for debugging sync issues
- Force acknowledge project structure to prevent 'Cannot sync a model as a place' errors

src/cli/sourcemap.rs

@@ -76,7 +76,7 @@ impl SourcemapCommand {
         let vfs = Vfs::new_default();
         vfs.set_watch_enabled(self.watch);
 
-        let session = ServeSession::new(vfs, project_path)?;
+        let session = ServeSession::new(vfs, project_path, None)?;
         let mut cursor = session.message_queue().cursor();
 
         let filter = if self.include_non_scripts {