Plan and execute CivicTheme upgrades in Drupal projects. Use when working with Drupal sites using CivicTheme that need version upgrades (e.g., 1.10→1.11, 1.11→1.12). Handles SDC migration, Twig syntax updates, build tooling changes, and customisation preservation. Triggers include "upgrade civictheme", "civictheme migration", "update civictheme version", or any CivicTheme-related Drupal theme upgrade work.