📝 Check off the CI TypeScript-floor task

The backlog item asked for a 5.0 baseline; the floor is 5.9 (set by type-fest
and the library's own gate), so the text now says "the TypeScript floor".

backlog.tasks

@@ -22,4 +22,4 @@ Maintenance:
     ☐ Add a minimal dir-listing webserver to the gitea docker setup for serving landing page (reuse existing reverse proxy)
     ☐ CI writes landing page to a shared volume keyed by project + tag (e.g. `/landing/tiny-pattern-ts/<tag>/`)
     ☐ Browse to `…/tiny-pattern-ts/index.html` in the browser
-☐ Add testing with TypeScript 5.0 baseline in CI
+✔ Add testing with the TypeScript floor in CI @done