docs: add Contract sections + tag tests to contract items (Tier 2 — 10 files)

org/core-skills.org

@@ -25,6 +25,14 @@ After loading, the engine exports the skill's public symbols into the ~passepart
 
 This is how the "thin org, fat skills" principle works in practice: the org provides the loading infrastructure; the skills provide all the intelligence.
 
+** Contract
+
+1. (lisp-syntax-validate code-string): returns T if the Lisp code is
+   structurally valid, nil if reader errors are detected.
+2. (skill-topological-sort dir): reads org files in a directory, parses
+   ~#+DEPENDS_ON:~ declarations, returns files sorted such that
+   dependencies come before dependents.
+
 * Implementation
 
 ** Package Context
@@ -425,6 +433,7 @@ Verifies that the topological sorter correctly orders skills by their ~#+DEPENDS
 (in-suite boot-suite)
 
 (test test-topological-sort-basic
+  "Contract 2: dependency ordering puts dependencies before dependents."
   (let ((tmp-dir "/tmp/passepartout-boot-test/"))
     (uiop:ensure-all-directories-exist (list tmp-dir))
     (with-open-file (out (merge-pathnames "org-skill-a.org" tmp-dir) :direction :output :if-exists :supersede)
@@ -439,10 +448,10 @@ Verifies that the topological sorter correctly orders skills by their ~#+DEPENDS
        (uiop:delete-directory-tree (uiop:ensure-directory-pathname tmp-dir) :validate t))))
 
 (test test-lisp-syntax-validate-valid
-  "Valid Lisp code should pass syntax validation."
+  "Contract 1: valid Lisp code passes syntax validation."
   (is (eq t (lisp-syntax-validate "(+ 1 2)"))))
 
 (test test-lisp-syntax-validate-invalid
-  "Unbalanced Lisp code should fail syntax validation."
+  "Contract 1: unbalanced Lisp code fails syntax validation."
   (is (null (lisp-syntax-validate "(+ 1 2"))))
 #+end_src