Add Creative Writing expansion pack (#414)

* Add Creative Writing expansion pack
- 10 specialized writing agents for fiction and narrative design
- 8 complete workflows (novel, screenplay, short story, series)
- 27 quality checklists for genre and technical validation
- 22 writing tasks covering full creative process
- 8 professional templates for structured writing
- KDP publishing integration support

* Fix bmad-creative-writing expansion pack formatting and structure

- Convert all agents to standard BMAD markdown format with embedded YAML
- Add missing core dependencies (create-doc, advanced-elicitation, execute-checklist)
- Add bmad-kb.md customized for creative writing context
- Fix agent dependency references to only include existing files
- Standardize agent command syntax and activation instructions
- Clean up agent dependencies for beta-reader, dialog-specialist, editor, genre-specialist, narrative-designer, and world-builder

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Co-authored-by: Brian <bmadcode@gmail.com>

expansion-packs/bmad-creative-writing/tasks/brainstorm-premise.md

@@ -0,0 +1,16 @@
+# ------------------------------------------------------------
+# 1. Brainstorm Premise
+# ------------------------------------------------------------
+---
+task:
+  id: brainstorm-premise
+  name: Brainstorm Premise
+  description: Rapidly generate and refine one‑sentence log‑line ideas for a new novel or story.
+  persona_default: plot-architect
+steps:
+  - Ask genre, tone, and any must‑have elements.
+  - Produce 5–10 succinct log‑lines (max 35 words each).
+  - Invite user to select or combine.
+  - Refine the chosen premise into a single powerful sentence.
+output: premise.txt
+...