TUI Plugin sharing - add remote plugin identity

[canvrno-oai]

This starts the shared-plugin TUI stack by teaching the existing plugin popup flows to address plugins from either a local marketplace path or a remote marketplace name. The visible surface stays intentionally narrow so later catalog work can build on stable remote request identity without adding share-management UI.

• Adds remote-capable detail/install/uninstall request routing for plugin popup actions.
• Uses remote plugin IDs for remote install and uninstall while preserving local plugin IDs and paths.
• Keeps remote detail views available when a marketplace has no filesystem path.
• Blocks admin-disabled plugin installs and toggle affordances in the existing flows.
• Validation: not run; this was a branch split/publish pass.