feat: surface Comet-managed changes and recommended archive commands

[jacobleft]

🔎 Existing issue check

• I have searched the existing issues.

🧭 Problem

In a mixed OpenSpec/Comet workflow, some active changes are plain OpenSpec changes while others include .comet.yaml and should be archived through Comet to preserve lifecycle metadata and annotate Superpowers docs.

In practice this required manual inspection:

• Plain OpenSpec change: openspec archive <change> -y
• Comet-managed change: node "$COMET_ARCHIVE" <change>

openspec list showed both as complete, but did not indicate which changes were Comet-managed or recommend the correct archive command.

✨ Proposed solution

Provide a Comet status/list view that classifies active changes and recommends the archive route, for example:

change-name   complete   comet-managed=yes   recommended: comet archive change-name
other-change  complete   comet-managed=no    recommended: openspec archive other-change -y

Or expose structured JSON via comet status --json:

{
  "change": "...",
  "cometManaged": true,
  "recommendedArchiveCommand": "comet archive ..."
}

🎯 Primary area

Classic workflow runtime (domains/comet-classic, assets/skills/comet/scripts/)

🪐 Workflow phase

Archive

🔀 Alternatives considered

Manually inspect whether openspec/changes/<name>/.comet.yaml exists and choose either Comet archive or OpenSpec archive. This is error-prone and easy to miss when multiple complete changes are active.

🧰 Compatibility notes

• Comet package: @rpamis/comet@0.4.0-beta.3
• OpenSpec CLI: @fission-ai/openspec@1.5.0
• Mixed plain OpenSpec and Comet-managed changes can exist in the same repo.

🧩 Additional context

If comet archive is invoked on a plain OpenSpec change, it could either delegate safely or print the proper command.