Support updating plugins installed from custom marketplaces

What feature would you like to see?

Plugins installed from a custom marketplace (/plugins marketplace <source> / KIMI_CODE_PLUGIN_MARKETPLACE_URL) are snapshotted into plugins/managed/<id>/ at install time and never track the source again. The only way to pick up a new version is to manually reinstall each plugin.

It would help to have:

• A /plugins update <id> (and/or /plugins update --all) command that re-fetches the source and upgrades in place
• Update availability surfaced in the /plugins manager for plugins installed from a custom marketplace, similar to how official/curated plugins show updates
• Optionally, a way to refresh the marketplace catalog itself (e.g. re-fetch the marketplace JSON on demand)

Additional information

Context: I maintain a custom marketplace to distribute internal plugins to my team. Every release today means asking each team member to manually reinstall plugins, which doesn't scale.

Other coding-agent harnesses with plugin marketplaces support refreshing/updating marketplace plugins, so teams evaluating Kimi Code alongside them feel this gap.

Current version: kimi --version → 0.33.0

Start by tracing the /plugins marketplace <source> installation flow, the /plugins manager, and the plugins/managed/<id>/ storage path; inspect how KIMI_CODE_PLUGIN_MARKETPLACE_URL sources are recorded and how official plugin updates are detected. Done means a custom-marketplace plugin can be refreshed and updated by id or in bulk, with update availability shown in the manager, and marketplace catalog refresh behavior is defined.