Allow me to install Claude Code locally for devcontainer

I run my devcontainers as the vscode user to minimize blast radius of Claude Code in the devcontainer.

Because of this, the auto update fails to work because claude code is installed globally so the vscode user does not have permissions to update it.

There is a /migrate-installer command that will fix this but if I rebuild the container because of a change, I go back to the old install location and the updater is broken again.

Fix:
Add a `"installAsUser": true` that installs claude code into the same location that /migrate-installer does.

Thanks!