Handle reentrant theme subscriptions, add retained-frame browser coverage, and align the authoring example with the advisory appearance contract.
Co-authored-by: Ouroboros <311266734+ouroboros-agent@users.noreply.github.com>
`ruff check . --select F` (a blocking quick-test step) flagged the imported
`subscription_ui` pytest fixture in tests/test_theme_browser.py as unused
(F401): fixtures are requested by parameter name, which pyflakes cannot
see. Use the repository's existing re-export idiom
(tests/test_plan_author_presentation.py) instead of a noqa.
Co-authored-by: Ouroboros <311266734+ouroboros-agent@users.noreply.github.com>
