Use whenever the user wants to change data inside a ConfigHub Unit — update an image, adjust replicas, set environment variables, add labels/annotations, change a resource field, apply defaults, or make a bulk edit across many units. This skill enforces the "prefer a function over a hand-edit" rule, composes a proper change description that captures the user's prompt and clarifications, and chooses between `cub function set` (single function, targeted or bulk) and `cub unit update` (whole-unit replacement or restore). Load proactively any time the user says "update the image", "bump the replicas", "change the env var", "set the annotation", "apply defaults", "edit this unit", or any natural request that will end in a write to ConfigHub. Do not load for: creating a brand-new Unit (use config-as-data), reading/inspecting config (use cub-query), or setting up validation (use triggers-and-applygates).