drop the unused mocktail dep; amend D-25 (T-385)

mocktail was pinned and documented as the IO-mocking strategy, but
after the T-91 coverage drive it had zero imports — every IO seam
ended up with an injected hand-rolled fake instead. D-25 is amended
to record that the hand-rolled-fakes rule covers IO seams too;
licenses.yaml and the lockfile follow. The ptyc binary removal noted
in this sweep landed with the git-API commit (it was already staged).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pubspec.lock

@@ -338,14 +338,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.0"
-  mocktail:
-    dependency: "direct dev"
-    description:
-      name: mocktail
-      sha256: "5e1bf53cc7baa8062a33b84424deb61513858ea05c601b8509e683815b5914aa"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.5"
   node_preamble:
     dependency: transitive
     description: