Agent Skills: fable-like-implementation

Use when the session model is Opus 4.8 (claude-opus-4-8) and the user asks to build, add, implement, refactor, migrate, or integrate something non-trivial — 3+ files, a new dependency or subsystem, an API contract or database schema change, or meaningful ambiguity or risk — or says "plan this out", "spec this", "how should we build", "create an implementation plan". Also use when the user says "just implement it" but the work is non-trivial. Do NOT use on Claude Fable 5 or any other model, nor for one-line fixes, typo corrections, single-function changes, or questions that require no code change.