Add nodes/prompt_builder_node.py: PromptBuilderNode, a thin adapter that
delegates to build_prompts (MASTER_SPEC §20, §19).
- Input category_map (CATEGORY_MAP); optional config (COMPILER_CONFIG) defaulting
to Config().
- Emits 21 STRING outputs: one per canonical category (in order) plus the
reserved `negative` and `scene` outputs (always empty in V1). Values are keyed
by output name so wiring stays stable. No compiler logic in the node.
- Registered as SceneCompilerPromptBuilder ("Prompt Builder").
Tests: 21-output metadata, comma formatting + ordering + empty-category strings,
reserved-empty outputs, custom separator via config, and registration.
Co-authored-by: kunail0804 <kunail0804@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>