feat(agents): show last used by/at on card and settings

[rafavalls]

What is this contribution about?

Surfaces "last used" information for agents in two places: the agent card footer (grid/list view) and the agent settings page. Data is derived from the most recent thread created for each agent — no schema migration required.

• Card footer: shows "Last used X ago" when threads exist, falls back to "Updated X ago"
• Settings page: single metadata line below the identity header — [avatar] Name · Created May 6 · Last used X ago — with a second avatar shown inline only when the last user differs from the creator
• VirtualMCPEntity: two new optional fields last_used_at / last_used_by populated via a DISTINCT ON query against the threads table
• User component: new nameClassName prop to allow callers to override the hardcoded font-medium on the name text

Screenshots/Demonstration

Agent card footer and settings metadata line updated — see PR description above.

How to Test

1. Open the agents grid — cards with existing threads show "Last used X ago" in the footer
2. Click into any agent settings — the metadata line below the header shows creator + created date + last used time
3. For agents with no threads, the card shows "Updated X ago" and settings shows "Never used"

Migration Notes

No database migrations required. last_used_at and last_used_by are computed at read time from the existing threads table.

Review Checklist

• PR title is clear and descriptive
• Changes are tested and working
• Documentation is updated (if needed)
• No breaking changes

---

Summary by cubic

Show the “last used” time and user for each agent in the card footer and on the settings page, based on the latest thread. Adds last_used_at and last_used_by to the entity and SDK; no migration needed.

• New Features
  • Card footer shows “Last used X ago”; falls back to “Updated X ago”.
  • Settings metadata shows creator, created date, and “Last used X ago” (or “Never used”).
  • Backend computes last usage via a DISTINCT ON query on threads and returns last_used_at/last_used_by in both single and list fetches.

^{Written for commit 87863ef. Summary will update on new commits.}

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Release Options

Suggested: Minor (2.311.0) — based on feat: prefix

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Reaction	Type	Next Version
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🚀	Major	3.0.0

Current version: 2.310.0

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