[Bug] Desktop app: after adding a GitHub plugin marketplace, it can't be found or installed

Adding a plugin marketplace from GitHub via the Desktop app appears to be broken. Reproduced with:

https://github.com/makenotion/claude-code-notion-plugin.git

After adding this marketplace through the Desktop app:

• ~/.claude/plugins/known_marketplaces.json and extraKnownMarketplaces in settings.json correctly record the marketplace.
• The marketplace source is checked out locally under ~/.claude/plugins/marketplaces/notion-plugin-marketplace/, and the plugin files are already present in ~/.claude/plugins/cache/notion-plugin-marketplace/notion-workspace-plugin/0.1.0/.
• But in the Desktop app UI itself, I cannot find the marketplace anywhere, searching for it or its plugin by name returns nothing, and there is no UI to install/enable a plugin from it.
• enabledPlugins in settings.json never gets an entry for the plugin, even though the plugin files are already cached locally.

The terminal's /plugin menu at least lists this marketplace (it reads known_marketplaces.json directly from disk), but doesn't complete installation/enabling either. So the practical effect is: adding a marketplace via the Desktop app never results in a usable, enabled plugin, in either the Desktop app or the terminal.

Environment: macOS 15.7.3 (24G419), Claude Code version 2.1.263 (per ~/.claude.json record, may not be exact).

Expected behavior: After adding a marketplace via the Desktop app, it should be visible/searchable in the app, with a working UI to install and enable its plugins.