Landlord Initiated The Move-out Process Without A Written Notice (wa)

Location: Washington state, USA

My landlord has started the move-out process without a written notice from me (specifically required in my lease and by WA law) after taking a sentence that I said in passing from more than 6 months ago ("I plan to move out sometime in May/June") as my notice to end my tenancy. I received a letter in late March sent via certified mail that said, "Thank you for informing me of your plan to move out this coming June," but I never sent a written notice with my intent to vacate the apartment. I sent an email asking about this and stating that my plans had changed to moving out closer to October 2026 (but was not my written notice; I hope to be out of this apartment around August). They responded a week later with what I thought was a blank email sent in error, and I did not follow up with an email asking about the blank reply like I probably should have. In actuality, they did respond but it was in all white text (probably copied and pasted from a notes app or other source in dark mode, I'm guessing?). I did not realize that they had responded, and was surprised to get a move-out packet last week sent via certified mail, setting my move-out date as the end of June.

This is going to take a lot of effort and time to battle, and I'm not sure it is worth it to stay six more months in a place I don't want to be in with a landlord that has always been dismissive and openly rude to me.

Am I right in that my landlord is violating my lease and WA state laws? I am seeking local resources to help with possible mediation, but I don't know how else to enforce my right to end my tenancy instead of being bullied out of it. Any advice or suggestions are appreciated in advance.