0.6.3 — the details popup, and a filter that only claims its own upgrade

Fixed

• "View details" opened on an error. The details thickbox — and the View version x.y.z details link that sits right next to the update button — goes to the wordpress.org API, which has never heard of this plugin, so it answered An unexpected error occurred. That is the worst possible moment for it: the reader is deciding whether to trust the update. The pack now answers plugins_api for its own slug with the plugin header data and the release notes from the payload it already cached, so the popup costs no extra request. The notes go through a deliberately tiny Markdown pass (headings, bold, code, list items) applied after escaping, so anything unexpected from the API shows up as text instead of markup.
• upgrader_source_selection matched by substring. The filter runs for every plugin and theme upgrade on the site, and str_contains( $plugin, 'unofficial-abilities-for-breakdance-elements' ) would also claim an upgrade of any plugin whose slug contains this one's. It now compares plugin_basename() exactly, against the new BDOX_PACK_FILE constant.