Who allocates & who frees

Resource	Allocation point	Freed by
Input line (char *input)	readline() or get_next_line()	main_loop()
Token list (t_token *)	tokenize()	process_input() (free_token_list())
Token value (token->value)	tokenize() (extraction)	free_token()
Expanded value	expand_variables(), expand_full()	expand_all_tokens() (frees old, stores new)
AST tree (t_ast *)	parse_pipeline() functions	process_input() (free_ast())
AST cmd.args	collect_args() (malloc + ft_strdup)	free_ast() -> free_args()
AST redir.file	Parser (ft_strdup(token->value))	free_ast() -> free(file)
Env list (t_env *)	init_env()	main() (free_env_list())
Env node key/value	create_env_node() (ft_substr/ft_strdup)	free_env_list() or remove_env_node()
Command path (char *path)	find_cmd_path()	exec_external() (free(path))
Env array (char **envp)	env_to_array()	exec_external() (ft_free_strarray())
GNL internal stash	get_next_line()	get_next_line(-42)

Pipe children memory cleanup

Forked children in exec_left_pipe_child() / exec_right_pipe_child() inherit all parent memory.
Before calling exit() they free:

shell->current_input
shell->current_ast
shell->env
GNL stash

This prevents some of the valgrind "still reachable" reports

Tracked pointers in t_shell

shell->current_ast and shell->current_input are set during execution and cleared after.
They exist only so that forked pipe children can free inherited memory before exit.