Update the per-user-profile plan document to reflect the corrected Task 3
design: remove the now-unreachable TestClaimLegacyOwner_NoOpOnGenuinelyFreshInstall
test from the code example, update the ClaimLegacyOwner implementation example to
remove the dead-code branch and false doc comment about fresh installs, and fix
the commit message to match the corrected design.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>