Save The Tree implementation and acceptance work in progress

Preserve production code, regression fixtures, audio assets and provenance, test infrastructure, and the original-completion plan and progress ledger. Final game and Windows acceptance remain pending; excluded local artifacts and native experiments are not part of this snapshot.

scripts/core/command_queue.gd

@@ -76,13 +76,14 @@ func drain_ready(current_tick: int) -> Array[SimulationCommand]:
 			break
 		_pending.pop_front()
 		_in_flight[command.command_id] = command
-		ready.append(command)
+		ready.append(command.copy())
 	return ready
 
 
 func execute_ready(current_tick: int, executor: Callable) -> Array[CommandResult]:
 	var results: Array[CommandResult] = []
 	for command in drain_ready(current_tick):
+		var accepted_command_id := command.command_id
 		var result: CommandResult
 		if not executor.is_valid():
 			result = CommandResult.failed(
@@ -103,10 +104,8 @@ func execute_ready(current_tick: int, executor: Callable) -> Array[CommandResult
 					"Executor did not return a successful CommandResult."
 				)
 
-		if result.command_id == 0:
-			result.command_id = command.command_id
-		complete(command.command_id, result)
-		results.append(result.copy())
+		var completed_result := complete(accepted_command_id, result)
+		results.append(completed_result)
 	return results
 
 
@@ -164,6 +163,14 @@ func processed_count() -> int:
 	return _processed_results.size()
 
 
+## Read only pending commands, without serializing the processed history.
+func get_pending_commands() -> Array[SimulationCommand]:
+	var result: Array[SimulationCommand] = []
+	for command: SimulationCommand in _pending:
+		result.append(command.copy())
+	return result
+
+
 func get_accepted_command_metadata() -> Array[Dictionary]:
 	var result: Array[Dictionary] = []
 	var command_ids: Array = _accepted_metadata.keys()