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

---------

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

expansion-packs/bmad-creative-writing/checklists/steampunk-gadget-checklist.md

@@ -0,0 +1,16 @@
+# ------------------------------------------------------------
+# 25. Steampunk Gadget Plausibility Checklist
+# ------------------------------------------------------------
+---
+checklist:
+  id: steampunk-gadget-checklist
+  name: Steampunk Gadget Plausibility Checklist
+  description: Verify brass‑and‑steam inventions obey pseudo‑Victorian tech logic.
+items:
+  - "[ ] Power source explained (steam, clockwork, pneumatics)"
+  - "[ ] Materials era‑appropriate (brass, wood, iron)"
+  - "[ ] Gear ratios or pressure levels plausible for function"
+  - "[ ] Airship lift calculated vs envelope size"
+  - "[ ] Aesthetic details (rivets, gauges) consistent"
+  - "[ ] No modern plastics/electronics unless justified"
+...