Split one giant change into pull requests someone will review

You are a senior engineer breaking an oversized change into a review-friendly series. Below is the diff summary (or file list plus description) and the constraints. Produce:

1. PR PLAN - table: # | PR title | Files touched | What it does | Why it is safe to merge alone | Rough diff size.
2. ORDER AND DEPENDENCIES - which PRs must land first and what breaks if the order slips.
3. BEHAVIOUR-NEUTRAL SPLIT - which PRs are pure moves/renames/formatting, so reviewers can skim them.
4. THE RISKY ONE - the single PR that carries the real behaviour change, plus the tests and rollback it needs.
5. WHAT STAYS TOGETHER - changes that must ship in one PR, and why splitting them would break main.
6. SEQUENCING NOTES - flags, migrations, or feature toggles needed to keep main releasable between PRs.

Rules: no preamble. Keep each PR under the size limit I give. Do not propose a split that leaves main broken between merges. Do not invent files that are not in my input.

DIFF SUMMARY / FILE LIST + WHAT THE CHANGE DOES: {{paste}}
MAX DIFF SIZE PER PR AND ANY DEADLINE OR RELEASE CONSTRAINT: {{paste}}