Resign professionally, with a letter and a handover plan

I am resigning from my job and want to do it professionally. Help me write a short resignation letter and plan the conversation with my manager and the handover.

My role and team: {{my_role}}
My manager: {{manager_name}}
My intended last day: {{last_day}}
Notice period in my contract or handbook, or "not sure": {{notice_terms}}
What I am willing to say about why I am leaving, or "nothing": {{shareable_reason}}
How I would respond to a counteroffer: {{counteroffer_stance}}

My current work, recurring tasks, accounts, and who might take each over:
"""
{{current_work}}
"""

Task: Give me four parts.
1. The resignation letter, 80 to 150 words in a gracious, professional tone: that I am resigning, my role and my last day, a brief thank-you, and an offer to help with the handover. Leave out complaints, detailed reasons and anything emotional, because the letter goes in my file and may be read years later.
2. Talking points for telling my manager in person or on a call before I send the letter: four or five points in order, plus short answers to "Why are you leaving?" (using only what I am willing to share) and to a counteroffer, in line with my stance above.
3. A handover plan: a table with the columns Item, Status, Where it lives, Proposed owner, What is left to do by my last day, followed by a week-by-week plan up to my last day.
4. A checklist of things to confirm before I leave: final pay and unused vacation, when benefits end, my retirement plan, equipment to return, personal files, and any agreements I signed, such as confidentiality or non-compete terms.

Rules:
- Do not name my new employer or give reasons I did not mark as shareable.
- Do not state a notice period or any legal right. If the notice terms say "not sure", tell me to check my contract or ask HR, and write [last day] in the letter if the date depends on it.
- Present the checklist as questions for HR, my contract or a qualified advisor. It is not legal advice.

If anything is unclear or missing in my list of current work, do not guess: build the handover table from what is there and add the questions I should answer to complete it.