refactor bk2->tasproj conversion

- don't mutilate the bk2movie during the conversion
- don't immediately set MovieSession.Movie without having loaded the taproj

src/BizHawk.Client.Common/movie/MovieConversionExtensions.cs

@@ -16,8 +16,6 @@ namespace BizHawk.Client.Common
 			tas.CopyLog(old.GetLogEntries());
 			tas.LogKey = old.LogKey;
 
-			old.Truncate(0); // Trying to minimize ram usage
-
 			tas.HeaderEntries.Clear();
 			foreach (var (k, v) in old.HeaderEntries) tas.HeaderEntries[k] = v;
 

src/BizHawk.Client.Common/movie/MovieSession.cs

@@ -294,13 +294,6 @@ namespace BizHawk.Client.Common
 			Movie = null;
 		}
 
-		public void ConvertToTasProj()
-		{
-			Movie = Movie.ToTasMovie();
-			Movie.Save();
-			Movie.SwitchToPlay();
-		}
-
 		public IMovie Get(string path, bool loadMovie)
 		{
 			// TODO: change IMovies to take HawkFiles only and not path

src/BizHawk.Client.Common/movie/interfaces/IMovieSession.cs

@@ -85,11 +85,6 @@ namespace BizHawk.Client.Common
 
 		void StopMovie(bool saveChanges = true);
 
-		/// <summary>
-		/// If a movie is active, it will be converted to a <see cref="ITasMovie" />
-		/// </summary>
-		void ConvertToTasProj();
-
 		/// <summary>
 		/// Create a new (Tas)Movie with the given path as filename. If <paramref name="loadMovie"/> is true,
 		/// will also attempt to load an existing movie from <paramref name="path"/>.

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.cs

@@ -247,8 +247,8 @@ namespace BizHawk.Client.EmuHawk
 					return false;
 				}
 
-				ConvertCurrentMovieToTasproj();
-				success = StartNewMovieWrapper(CurrentTasMovie, isNew: false);
+				var tasMovie = ConvertCurrentMovieToTasproj();
+				success = LoadMovie(tasMovie);
 			}
 
 			// Start Scenario 2: A tasproj is already active
@@ -473,10 +473,11 @@ namespace BizHawk.Client.EmuHawk
 			}
 		}
 
-		private void ConvertCurrentMovieToTasproj()
+		private ITasMovie ConvertCurrentMovieToTasproj()
 		{
-			MovieSession.ConvertToTasProj();
-			Settings.RecentTas.Add(MovieSession.Movie.Filename);
+			var tasMovie = MovieSession.Movie.ToTasMovie();
+			tasMovie.Save(); // should this be done?
+			return tasMovie;
 		}
 
 		private bool LoadMovie(ITasMovie tasMovie, bool startsFromSavestate = false, int gotoFrame = 0)