Plugin skills not shown in CLI autocomplete dropdown

Description

Plugin-defined skills are correctly loaded into context and work when invoked programmatically (via the Skill tool or by typing the full name), but they do not appear in the CLI autocomplete dropdown when the user types /.

Expected behavior

When typing / in the Claude Code CLI, plugin skills should appear alongside built-in commands and project-level skills in the autocomplete dropdown.

Actual behavior

• Built-in commands (/help, /compact, etc.) appear in autocomplete ✓
• Project-level skills (from .claude/skills/) appear in autocomplete ✓
• Plugin skills do not appear in autocomplete ✗

The plugin skills ARE loaded into context (confirmed via /context), use minimal tokens (~191 tokens total for 9 skills), and function correctly when invoked by the model. They just aren't discoverable through the autocomplete UI.

Steps to reproduce

1. Install a plugin that provides skills (e.g., via a marketplace with skills/ directory containing SKILL.md files)
2. Confirm the plugin is enabled in settings.json under enabledPlugins
3. Start a new Claude Code session
4. Run /context — plugin skills are listed under "Skills > Plugin"
5. Type / — only built-in commands and project-level skills appear in autocomplete
6. Type /plugin-name:skill-name — no autocomplete suggestion appears

Environment

• macOS (Darwin 25.2.0)
• Plugin installed globally (user scope)
• Plugin structure: standard skills/ directory with SKILL.md files per skill
• Skills have standard frontmatter (name, description)

Workaround

Users can type the full skill name (e.g., /stemago-tools:reflect) and submit — the model recognizes and executes it. But discoverability suffers without autocomplete.