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

lisp/system-diagnostics.lisp

@@ -185,12 +185,12 @@
 (in-suite diagnostics-suite)
 
 (test test-diagnostics-dependency-fail
-  "Verify that missing binaries are correctly identified as failures."
+  "Contract 1: missing binaries cause diagnostics-dependencies-check to return nil."
   (let ((passepartout::*diagnostics-binaries* '("non-existent-binary-123")))
     (is (null (diagnostics-dependencies-check)))))
 
 (test test-diagnostics-env-fail
-  "Verify that an invalid MEMEX_DIR triggers a critical failure."
+  "Contract 2: invalid MEMEX_DIR causes diagnostics-env-check to return nil."
   (let ((old-m (uiop:getenv "MEMEX_DIR"))
         (old-d (uiop:getenv "PASSEPARTOUT_DATA_DIR")))
     (unwind-protect
@@ -201,7 +201,7 @@
       (setf (uiop:getenv "PASSEPARTOUT_DATA_DIR") (or old-d "")))))
 
 (test test-diagnostics-dependency-success
-  "When all binaries exist, diagnostics should pass."
+  "Contract 1: all binaries present returns T."
   (let ((passepartout::*diagnostics-binaries* '("ls")))
     (is (eq t (diagnostics-dependencies-check)))))