Use UUIDs instead of indices for branch params in new functions

Author: YoshiRulz

src/BizHawk.Client.EmuHawk/tools/Lua/Libraries/TAStudioLuaLibrary.cs

@@ -462,10 +462,10 @@ public void LoadBranch(int index)
 		}
 
 		/// <remarks>assumes a TAStudio project is loaded</remarks>
-		private TasMovieMarkerList/*?*/ MarkerListForBranch(int? branchIndex)
-			=> branchIndex is int i
-				? Tastudio.CurrentTasMovie.Branches.ElementAtOrDefault(i)?.Markers
-				: Tastudio.CurrentTasMovie.Markers;
+		private TasMovieMarkerList/*?*/ MarkerListForBranch(string/*?*/ branchID)
+			=> Guid.TryParseExact(branchID, format: "D", out var parsed)
+				? Tastudio.CurrentTasMovie.Branches.FirstOrDefault(branch => branch.Uuid == parsed)?.Markers
+				: branchID is null ? Tastudio.CurrentTasMovie.Markers : null; // not a typo; null `branchID` indicates main log
 
 		[LuaMethodExample("""
 			local marker_label = tastudio.getmarker(tastudio.find_marker_on_or_before(100));
@@ -474,9 +474,9 @@ public void LoadBranch(int index)
 			name: "find_marker_on_or_before",
 			description: "Returns the frame number of the marker closest to the given frame (including that frame, but not after it)."
 				+ " This may be the power-on marker at 0. Returns nil if the arguments are invalid or TAStudio isn't active."
-				+ " If branchIndex is specified, searches the markers in that branch instead.")]
-		public int? FindMarkerOnOrBefore(int frame, int? branchIndex = null)
-			=> Engaged() && MarkerListForBranch(branchIndex) is TasMovieMarkerList markers
+				+ " If branchID is specified, searches the markers in that branch instead.")]
+		public int? FindMarkerOnOrBefore(int frame, string/*?*/ branchID = null)
+			=> Engaged() && MarkerListForBranch(branchID) is TasMovieMarkerList markers
 				? markers.PreviousOrCurrent(frame)?.Frame
 				: null;
 
@@ -486,9 +486,9 @@ public void LoadBranch(int index)
 		[LuaMethod(
 			name: "get_frames_with_markers",
 			description: "Returns a list of all the frames which have markers on them."
-				+ " If branchIndex is specified, instead returns the frames which have markers in that branch.")]
-		public LuaTable GetFramesWithMarkers(int? branchIndex = null)
-			=> Engaged() && MarkerListForBranch(branchIndex) is TasMovieMarkerList markers
+				+ " If branchID is specified, instead returns the frames which have markers in that branch.")]
+		public LuaTable GetFramesWithMarkers(string/*?*/ branchID = null)
+			=> Engaged() && MarkerListForBranch(branchID) is TasMovieMarkerList markers
 				? _th.EnumerateToLuaTable(markers.Select(static m => m.Frame))
 				: _th.CreateTable();