Replaces the static "Install plugin · N active" hero button with the
design's pair: a glass search input + a primary Install action. The
input is bound to a new InputState on ElyShell (plugin_search_input);
on every render the catalog reads its current value and filters the
plugin grid by case-insensitive contains on name, author, and
description. An empty-needle render shows every installed plugin so
the page still works at rest.
When the search yields no matches, the grid swaps to an empty-state
copy that quotes the user's needle. Install action moves into a
trailing dark chip that calls choose_plugin_package, preserving the
existing file-picker flow.
ZacharyZhang-NY
70b50f9852