Write a resignation letter that leaves on good terms

I'm resigning and I need a letter.

My job and manager: Account executive, reporting to Dana Whitfield
Notice and last day: Contract says four weeks. Last day would be Friday, October 23.
Why I'm leaving: Got a better offer elsewhere, more money and fully remote. Honestly I also stopped enjoying it after the reorganization, and Dana and I don't get on.
What I can offer on the way out: write handover notes for my accounts and introduce my replacement to the three biggest clients

Write the letter. Under 150 words.

Rules:
- The first sentence says I'm resigning and gives my last working day. Nothing before it.
- One line of thanks that's specific to this job, not a generic one.
- Say what I'll do for the handover.
- Leave out any complaint, criticism or detail about where I'm going, even if I mentioned it above. The letter goes in my file and might be read by someone I've never met.
- Plain and warm. No "it is with a heavy heart", no "I have decided to pursue other opportunities".

Then give me:
1. What to say in person before I send it, in two or three sentences, since my manager should hear it from me first.
2. If I mentioned a reason for leaving that's worth raising, whether an exit interview is the right place for it and how to say it without burning anything. If it isn't worth raising, say so.
3. Anything I should check before I send it, such as vacation days I'm owed or whether my notice date is right. Tell me what to check, not what the rules are, since that depends on my contract and where I live.

What you get: A short resignation letter, and what to say face to face before you hand it in.