Allocation Failure Contracts

Implement the documented-contract pair: ``c /* duplicates s into fresh heap memory; sets *out and returns 1 on success. Returns 0 WITHOUT touching *out on: NULL s, NULL out, or allocation failure. */ int safe_dup(const char *s, char **out); /* joins two strings into fresh memory "a/b" (separator always present); same contract as safe_dup. */ int path_join(const char *a, const char *b, char **out); ``

Difficulty: intermediate