--plugin-dir skills load but are omitted from /skills and /env #4886

Describe the bug

Skills supplied by a local plugin loaded with --plugin-dir are discovered by the backend but are omitted from the interactive /skills dashboard and /env output.

The same invocation's non-interactive copilot skill list --json output includes the plugin skills with "source": "plugin" and "enabled": true. Startup diagnostics also report plugin skills loaded with no skill errors or warnings. This suggests the interactive views are using a different or stale skill registry.

Affected version

GitHub Copilot CLI 1.0.86-1

Steps to reproduce the behavior

1. Create a local plugin such as C:\temp\sample-plugin with a root plugin.json containing "skills": "skills/".
2. Add a valid skill at skills/sample-skill/SKILL.md with name and description frontmatter.
3. Start an interactive session:

   copilot --experimental --plugin-dir "C:\temp\sample-plugin"

4. Run /env and /skills list in the interactive session.
5. In a separate terminal, run:

   copilot --experimental --plugin-dir "C:\temp\sample-plugin" skill list --json

6. Observe that the non-interactive command lists the enabled plugin skill, while /env and /skills list in the interactive session omit it.

Expected behavior

/env and /skills list should display every enabled plugin skill loaded into the interactive session, matching copilot skill list --json. Plugin-provided skills should also be available for explicit invocation.

Additional context

• Operating system: Windows 11 x64
• The plugin itself is listed as an enabled external plugin by copilot plugin list.
• Other plugin components load successfully.
• Skill diagnostics report no loading errors or warnings.
• This resembles earlier reports where plugin skills were usable or discovered internally but absent from the interactive skill inventory, but this reproduction uses an explicit local --plugin-dir plugin.