feat(cli): show plugin and skill readiness

[Babulubobo]

Description

Fixes #651.

Show READY and REASON in the default table output for arctl get plugins and arctl get skills, using the resource's Ready condition. When that condition is absent, show <none> in both columns; an empty reason also displays as <none>.

Add regression coverage for both resource kinds, including absent and unrelated conditions, True/False/Unknown states, empty reasons, and unchanged JSON output. Document the columns in the declarative CLI guide.

Change Type

/kind feature

Changelog

Add READY and REASON columns to plugin and skill list output, showing <none> when no Ready condition has been recorded.

Additional Notes

Local validation passed:

• make lint (0 issues).
• go test -tags=unit -timeout 5m ./....
• CLI build and subprocess smoke checks for plugin/skill table, JSON, YAML, named-resource, label-filter, and empty-list output.