[Cutover 2] Synchronize final v1 into v2 and approve the final release candidate

[draedful]

Goal

Prove that the final v2 release candidate contains every applicable final v1 change and is ready to replace v1 on main.

Scope

• Resolve every post-split v1 change through a sync PR or recorded no-port decision.
• Merge the final main state into v2 through a reviewed merge-commit pull request.
• Do not squash or rebase the sync.
• Record the source main SHA and resulting merge SHA.
• Audit the final merge and neutralize or explicitly resolve any non-applicable content covered by a no-port decision.
• Run the complete lint, typecheck, unit, package, Storybook, and E2E gates.
• Pack all v2 public packages and install them in isolated consumer fixtures.
• Verify intentional v1-to-v2 API changes against the current v1 contract.
• Publish and verify the final approved 2.x release candidate under next.
• Verify that the candidate does not update latest.
• Record the promotion pull request, go/no-go decision, and rollback point.

Acceptance criteria

• Every relevant v1 change has a sync PR or no-port decision.
• v2 contains the final main ancestry through the recorded merge commit.
• All source and artifact checks pass.
• The final release candidate is installed successfully from npm.
• The candidate remains under next.
• The cutover owner approves promotion.