fix: mock-forgejo path parsing bug + non-fatal cron in smoke-init (#586)

- Fix off-by-one in mock admin/users/{username}/repos path extraction
  (parts[4] was 'users', not the username — should be parts[5])
- Change _install_cron_impl to return 1 instead of exit 1 when crontab
  is missing, so cron failure doesn't abort entire init

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/ci-setup.sh

@@ -45,9 +45,9 @@ _install_cron_impl() {
 
   # Bare mode: crontab is required on the host
   if ! command -v crontab &>/dev/null; then
-    echo "Error: crontab not found (required for bare-metal mode)" >&2
+    echo "Warning: crontab not found (required for bare-metal scheduling)" >&2
     echo "  Install: apt install cron  /  brew install cron" >&2
-    exit 1
+    return 1
   fi
 
   # Use absolute path for the TOML in cron entries