chore(release): pin Claude Code to memhub v0.87.0

[sgonz-xtrace]

Moves the Claude Code catalog's pin from memhub--v0.76.0 (fcdc3b7) to memhub--v0.87.0 (5ac4962), the merge commit of #278.

• The tag was pushed before this PR, so ref resolves the moment this lands (git ls-remote shows 5ac49620… refs/tags/memhub--v0.87.0).
• plugins/memhub/.claude-plugin/plugin.json at 5ac4962 reads memhub 0.87.0.
• claude plugin validate . passes.

This is the Claude half of the 0.87.0 release. Codex and Cursor already got 0.87.0 when #278 merged, because their catalogs don't pin a version. Claude Code users keep getting 0.76.0 until this merges and they run /plugin marketplace update and restart.

🤖 Generated with Claude Code

[xtrace-memhub-staging]

🧠 Session context

1 session behind this pull request.

Team rules that fired while building this

• tests-before-push (advise, 12×)
• confirm-ambiguous-target (advise, 2×)
• Delegate big file reads to a cheaper model (gate, 2×)
• read-primary-source (advise, 2×)
• Release database sessions before LLM calls (advise, 2×)
• reuse-existing-mechanism (advise, 2×)
• …more

Effort
1 session · 3h 24m agent time · 95.4M tokens · 605 turns

Sessions

• release helper · Sebastian Gonzalez