Testing/CI/tooling consistency (#9,#20,#21,#22,#23,#28) (#59)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

modules/21-skills-teaching-the-ai-your-playbook/README.md

@@ -234,10 +234,13 @@ seen, producing all four parts without you listing the steps.
 
    ```bash
    git log --oneline add-command.md   # the procedure's own history
-   git diff HEAD~1 add-command.md      # if you tightened it in Part C — your workflow change as a diff
+   git log -p -- add-command.md        # full patch history: the file's creation, plus the Part C tighten if you made one
    ```
 
-   That diff *is* a change to how your team adds commands — readable, attributable, revertable. In a
+   (`git log -p` surfaces the skill's own patches no matter what you committed *after* tightening it —
+   unlike `git diff HEAD~1`, which would be empty here because the most recent commit added the second
+   *command*, not a change to the skill.) Each entry in that history *is* a change to how your team adds
+   commands — readable, attributable, revertable. In a
    team repo (Modules 8, 11) it reaches everyone on `git pull`; behind review (Module 10) it lands as a
    PR someone approves. You've turned a procedure you used to narrate into a versioned capability.