[FEATURE] Add sorting/filtering options to /plugin manager UI

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The /plugin command's "Installed" tab lists plugins grouped by scope (Project, Local, User) but within each group, plugins appear in the order they were defined in their marketplace JSON files. As the plugin ecosystem grows and users install more plugins, this list becomes harder to navigate.

Currently there's no way to:

• Sort plugins alphabetically, by enabled/disabled status, or by category
• Filter to show only enabled or only disabled plugins
• Reorder plugins by recently used or recently installed

With 10+ installed plugins across multiple marketplaces, finding and toggling a specific plugin requires scrolling through the entire list.

Proposed Solution

Add sort/filter controls to the /plugin Installed tab. For example:

• A keyboard shortcut (e.g., s to cycle sort modes) that sorts the list by:
• Name (A-Z / Z-A)
• Status (enabled first / disabled first)
• Source/Marketplace (group by marketplace)
• A filter toggle (e.g., f) to show:
• All plugins (default)
• Enabled only
• Disabled only

The existing bottom bar (type to search · Space to toggle · Enter to details · Esc to back) could be extended with these keybindings.

Alternative Solutions

• Searched for configuration files (settings.json, marketplace.json, installed_plugins.json) that might accept a sort order — none support this.
• Manually reordering entries in marketplace.json works temporarily but gets overwritten on marketplace sync/update.
• The search box helps for finding a known plugin by name, but doesn't help when browsing or bulk-managing plugins.

Priority

Low - Nice to have

Feature Category

Interactive mode (TUI)

Use Case Example

1. I have 15+ plugins installed from multiple marketplaces (awesome-claude-code-plugins, superpowers, official, etc.)
2. I want to quickly see which plugins are currently enabled
3. I open /plugin → Installed tab and see an unsorted list of all plugins
4. I have to scroll through the entire list and visually scan for the ✓ connected vs ○ disabled indicators, and i have to do this everytime
5. With sorting by status, I could press s to group all enabled plugins at the top, making it immediately clear what's active
6. With alphabetical sort, I could quickly jump to the plugin I'm looking for without relying on search

Additional Context

• The plugin list is currently ordered by the marketplace.json array order per marketplace, then grouped by scope (Project → Local → User)
• Plugin metadata already includes name and category fields that could be used as sort keys
• The settings.json file tracks enabled/disabled state, which could be used for status-based sorting