The CodeRabbit review of PR #15 flagged that playground/index.html had an
iframe src pointing to the feature/testing-framework branch. That URL fix
was applied in commit f48276c (updating to main branch).
This commit also removes the stale cache-busting `_t=2` query parameter
that was added during development. The blueprint URL now references the
canonical main branch path without any ephemeral query parameters.
Closes #36