Rewrite onboarding prose to a neutral voice

scripts/common.sh

@@ -63,7 +63,7 @@ repo_root() {
 }
 
 # Load $repo/.env into the environment.
-# Existing environment values take precedence (matches just's dotenv-load).
+# Existing environment values take precedence (matches dotenv-load in just).
 load_env() {
     local root env line key rest
     root="$(repo_root)"
@@ -111,6 +111,6 @@ require_cmd() {
 require_env() {
     local name="$1"
     if [ -z "${!name:-}" ]; then
-        die "environment variable '$name' is unset. Run 'just init-env' and fill .env."
+        die "environment variable '$name' is unset. Run 'just init-env'. Fill .env."
     fi
 }