feat(install): sideload grokbot plugins into Grok Bot's synced marketplace snapshot

[ScriptedAlchemy]

install grokbot now also mirrors the Cursor projection into the marketplace snapshot Grok Bot already syncs on its computer, matching official plugin layout:

• <agent-data>/plugins/marketplaces/github.com/<owner>/<repo>/<commit>/<plugin>/ + entry in that snapshot's .cursor-plugin/marketplace.json
• <agent-data>/plugins/cache/<owner>-<repo>/<plugin>/<commit>/ with .cache-complete

Target = bundle repository owner's marketplaces (override GROK_BOT_SIDELOAD_MARKETPLACE=owner/repo[,…], disable GROK_BOT_SIDELOAD=0). A plugin the hosted marketplace already ships at that commit is left alone. Re-running restores a pruned sideload. A record at <grokbot root>/agent-bundle/sideload/<plugin>.json lets uninstall grokbot remove exactly what was written (and only the marketplace entry it added). Plugin id remains server-assigned; next steps say so.

Tests: two new cases in tests/grokbot-install.test.ts (sideload+restore+uninstall; hosted-already + disabled).

[changeset-bot]

🦋 Changeset detected

Latest commit: 966766d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
agent-bundle	Minor
create-agent-bundle	Patch

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commit: 966766d