feat(paseo): preinstall nano and set the git identity from the environment

GIT_NAME and GIT_EMAIL expand into the four GIT_AUTHOR_*/GIT_COMMITTER_*
variables, the same shape code-server already uses. Passing the identity as
environment rather than running `git config` means agents and terminals commit
correctly with no setup step, and it does not depend on ~/.gitconfig surviving
in the /home/paseo volume.

paseo/compose.yml

@@ -8,6 +8,10 @@ services:
       - PASEO_PASSWORD=${PASEO_PASSWORD}
       - PASEO_HOSTNAMES=${PASEO_HOSTNAMES}
       - PASEO_TRUSTED_PROXIES=${PASEO_TRUSTED_PROXIES}
+      - GIT_AUTHOR_NAME=${GIT_NAME}
+      - GIT_AUTHOR_EMAIL=${GIT_EMAIL}
+      - GIT_COMMITTER_NAME=${GIT_NAME}
+      - GIT_COMMITTER_EMAIL=${GIT_EMAIL}
     volumes:
       - 'paseo-home:/home/paseo'
       - 'paseo-workspace:/workspace'