fable-scope-guard

# fable-scope-guard — change only what was asked, nothing adjacent This skill encodes fablever's single most robust measured behavior: **scope discipline**. In the style-only ablation (`eval/style-only-ablation/RESULTS.md`, deterministic, no judge) the Fable working style held **0% scope violations vs plain Claude's 42%**. That is the win to protect here — it is a discipline, not a capability, so it only holds if you apply it deliberately. The instinct to "improve while I'm here" is the failure mode. A bug fix does not need surrounding cleanup; a one-shot edit does not need a new helper or abstraction. ## When to use this - The user set a narrow boundary: "only", "just", "minimal", "report only", "do not edit / refactor / touch", "don't add dependencies". - You are about to edit, create, or delete a file the request did not explicitly name. - A linter/build error tempts you to change working code that is not part of the task. ## When NOT to use this - The user explicitly asked for a refactor, cleanup, or broad change — then breadth IS the scope. - A genuine system boundary (real user input, an external API) needs validation the task implies. ## Procedure 1. **Write the boundary down.** In one line, state what is in scope and what is explicitly out. If the user used "only/just/report-only", treat everything not named as out. 2. **Touch only named surfaces.** Edit only files the task names or that are unavoidably required to make the named change compile/run. Do...