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>

assets/licenses.yaml

@@ -205,15 +205,6 @@ dependencies:
 # Build-time-only dependencies — test runners, mocks, lints. Tracked
 # here for audit completeness; NOT rendered in the About screen.
 dev_dependencies:
-  - name: mocktail
-    kind: dart-package
-    version: "1.0.5"
-    homepage: https://pub.dev/packages/mocktail
-    license: MIT
-    purpose: >-
-      Mocks at IO / IPC boundaries. ChangeNotifier facades use
-      hand-rolled fakes instead of mocks (D-025).
-
   - name: alchemist
     kind: dart-package
     version: "0.12.1"