feat(paseo): select the terminal shell through SHELL

Paseo spawns terminals with process.env.SHELL and falls back to /bin/sh,
which is dash. It never consults the login shell, so chsh has no effect --
and would be reverted by the next rebuild regardless.

paseo/.env.example

@@ -23,3 +23,8 @@ PASEO_LABEL=paseo
 
 # Timezone for logs and agent shells.
 TZ=Asia/Ho_Chi_Minh
+
+# Shell for Paseo's terminals. Paseo reads $SHELL and falls back to /bin/sh
+# (dash), ignoring the user's login shell, so set it here rather than running
+# chsh -- which would be reverted by the next rebuild anyway.
+SHELL=/bin/zsh