How do I deal with someone else getting credit for my work?

You can prepare any legal document flawlessly, and then watch the attorney's name go on it while yours stays invisible. The resentment you feel is not petty. You did the work, and being unseen for good work is a real and common ache. There are two truths to hold at once. The credit line is the way this profession is built, and no amount of quiet excellence will change that structure from where you sit. But the skill itself is entirely yours, and no name on a page can take it. You know what you can do, and so do the people who work closely with you. Decide what you actually want from this. If it is more recognition or a bigger role, then let your work be the argument and ask plainly for the next step, more responsibility, a title, a path. If it is peace, then let your pride rest on the mastery itself. Feeding the resentment costs you more than it costs anyone who overlooked you.