[FEATURE] Grouping of Artifacts in the gallery

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

Artifacts cannot be grouped. The gallery is a flat list ordered by recent
activity, and the Artifact tool has no parameter for assigning an artifact
to a group.

Long-running projects produce many related artifacts (design plans, test
manuals, reports, worklogs). Retrieval depends on remembering a title or
scrolling the recency-ordered list. Related artifacts are interleaved with
unrelated ones as soon as any of them is updated.

Proposed Solution

• Allow users to create named groups in the Artifact gallery and assign

artifacts to one or more groups.

• Add an optional group parameter to the Artifact tool's publish action,

so that an agent can assign a new artifact to the project's group when
it is created.

• Add a group filter to the list action so that an agent can

enumerate the artifacts of one project.

• Groups are a classification only. Artifact URLs and sharing settings

are unchanged.

Alternative Solutions

1. A multi-file artifact with path prefixes gives a structure inside a

single URL, but only for pages designed as one document set.

1. A hand-written index artifact that links to the others. It must be

maintained manually and breaks when an artifact is replaced.

1. Pinning in the sidebar. Pinning is a flat list and does not scale

beyond a few items.

Tags or labels with the same semantics would also satisfy the use case,
provided they are filterable in both the gallery and the list action.

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

1. A repository accumulates plan, report, and test-manual artifacts over

several weeks.

1. After a few updates, artifacts from different topics are interleaved in

the gallery.

1. With grouping, the user opens the group for one topic and sees only its

artifacts; an agent publishes new ones directly into that group.

1. This removes the need to maintain a manual index artifact.

Additional Context

The Artifact tool currently exposes publish, list, read, delete, open,
pin, and unpin actions. None of them accepts a grouping attribute.