upstream sync: lists the tests enforce but the sync steps do not name #212

From PR #203 round 2 (sync-prompt lane simulated adding a skill, a playbook and a principle):

1. upstream-sync.yml step 3 says to add a README all-skills row for every new skill directory, but the test excludes principle-* and its failure message does not say so; add "non-principle" to the bullet and the message.
2. Tests enforce lists step 3 never names, failing with bare diffs: each playbook linked from docs/guide (test_static.py ~226), INDEX_SHAPED in tools/test_playbook_shape.py, the guide's principle counts (test_static.py ~158).
3. The /x spelling lint scans only tracked files, and step 7 runs the tools suite before git add -A, so an untracked new skill passes locally (CI catches it).
4. upstream-sync.yml:115-117 still hard-codes "twenty-five".