feat: Merge 05-Plot and 06-First Draft into 05-First Draft with YAML frontmatter

- Add YAML frontmatter support with split_yaml_frontmatter() in preprocess.rs
- Update create_scene_pair to create single merged files with YAML frontmatter
- Rename 06-First Draft to 05-First Draft and merge with 05-Plot content
- Update default_project_open_subdir to '05-First Draft'
- Add capitalizes filter to MiniJinja environment for template rendering
- Fix template placeholder escaping in CONSISTENCY.md
- Update all references from 06-First Draft and 05-Plot to 05-First Draft
- Update test expectations to match new folder structure

The merged approach uses YAML frontmatter (--- delimiters) at the top of
each draft file to store planning metadata, allowing it to be collapsed
in the editor while keeping all planning and draft content in one file.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

templates/snowflake/{{ cookiecutter.project_name }}/05-First Draft/Act 1/scene01.md

@@ -0,0 +1,128 @@
+---
+id: scene_01
+title: "Chapter One: The Beginning"
+slug: chapter-one-the-beginning
+act: 1
+chapter: 1
+scene: 1
+type: chapter
+status: draft
+word_count_target: 2000
+word_count_min: 1800
+word_count_max: 2200
+pov: ""
+characters: []
+setting: ""
+date: ""
+time: ""
+conflict: ""
+theme: ""
+tone: ""
+word_count: 0
+word_count_updated: ""
+session_word_count: 0
+last_session: ""
+total_sessions: 0
+version: 1
+created: ""
+updated: ""
+order: 1
+---
+
+# Chapter One: The Beginning
+
+**Scene File** | **ID:** scene_01 | **Status:** Draft
+
+---
+
+## Scene Metadata
+
+| Attribute | Value |
+|-----------|-------|
+| **Act** | 1 |
+| **Chapter** | 1 |
+| **Scene** | 1 |
+| **Type** | Chapter |
+| **POV** | Not set |
+| **Version** | 1 |
+| **Word Count Target** | 2000 |
+
+---
+
+## Word Count Tracking
+
+| Metric | Value |
+|--------|-------|
+| **Target** | 2000 |
+| **Minimum** | 1800 |
+| **Maximum** | 2200 |
+| **Current** | 0 |
+| **This Session** | 0 |
+| **Last Updated** | Never |
+
+---
+
+## Creative Elements
+
+### POV
+> Not specified
+
+### Characters
+
+### Setting
+> Not specified
+
+### Date & Time
+> Not specified | Not specified
+
+---
+
+## Story Structure
+
+### Conflict
+> Not specified
+
+### Theme
+> Not specified
+
+### Tone
+> Not specified
+
+---
+
+## Draft Content
+
+### Rough Draft:
+
+[Write your scene content here...]
+
+---
+
+## Writing Notes
+
+### Session Log
+| Date | Words Added | Notes |
+|------|--------------|-------|
+
+
+### Revision Notes
+- 
+- 
+
+---
+
+## Status Checklist
+
+- [ ] Planning complete
+- [ ] First draft complete
+- [ ] Word count target met
+- [ ] POV consistent
+- [ ] Character voices distinct
+- [ ] Setting details accurate
+- [ ] Conflict resolved/advanced
+- [ ] Ready for revision
+
+---
+
+**Created:**  | **Updated:** 
+