test(bigfive): scope personality warmup diff assertion

[fermatmind]

What changed

• limit the historical PERSONALITY-WARMUP-01 changed-line assertion to its original task branch
• keep runtime-freeze classifier coverage on main and future branches with the same two synthetic warmup Kernel lines

Why

After PR #3018 merged, origin/main has no Kernel diff, so the historical assertion incorrectly fails the repository full CI baseline. The classifier behavior itself remains valid and covered.

Validation

• focused historical assertion: 1 test, 1 assertion
• complete BigFiveResultPageV2CoreBodyPreviewTest: 334 tests, 699 assertions
• scoped Pint and git diff --check passed
• exact changed-file scope: one authorized test file

Intentionally deferred

• no manifest/state changes
• no runtime implementation changes
• no deployment or production operation

Repository rule impact

None. This is contract-test infrastructure only and does not change runtime authority or behavior.