What is the ruling on saying: "I have divorced you" (أنا طلقتك) and "I am divorcing you" (أنا مطلقك)? Is it an announcement of divorce or an initiation of it, and does it require intention?

There is no contradiction between a word being explicit for divorce and its being an informative statement (khabar) or a performative utterance (insha'). An explicit word for divorce is the term itself and its derivatives, provided it is not in the present or imperative tense. This word may be intended to enact a divorce or to inform about it. If it informs about it, it may be truthful or false. If the husband has not divorced his wife but falsely reports a divorce, no divorce occurs as a consequence of his lie.