Bopa 0.5.0

The library gives its space back to the notebooks.

• Navigate folders in the sidebar — it is now a folder tree, so a notebook is drawn once, on its cover in the grid, instead of twice.
• Reach every shelf control from the top right: + creates a notebook, the gear holds layout, sort, new folder, rename folder, Sync now, Trash and Settings.
• See more of the library at a glance: the header is two rows rather than four, with the folder toggle, breadcrumb, title and search in front of you.
• Read a folder's contents from its row — each one still counts everything filed directly inside it.

Validation: GitHub Actions on the release commit — NotableKit, the App unit tests on an iPad simulator including the XCUITest suite, the Mac Catalyst build, and the notable merge-vector check. All green; nothing was built locally.

Compatibility: no change to folders.json, notebook manifests, or the sync protocol. The Grid/List and sort preferences carry over from 0.4.0 — they moved into the gear menu, not into new storage.

This is a GitHub source release. It does not distribute an App Store or TestFlight build.