feat: Case format and skill drafts

- Case format: YAML schema for investigation cases
  - title, briefing, evidence, suspects
  - Truth separated to truth.enc (base64 encoded)
  - Images: path or URL

- Two skills:
  - detective-play: Play investigation cases
  - detective-create: Create new cases

- Folder structure:
  - ~/.hermes/detective/cases/ for all cases
  - Each case: case.yaml + truth.enc + images/

- Truth protection: base64 encoded, decode only after playing

docs/skills/detective-create/SKILL.md

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+---
+name: detective-create
+description: Create mystery investigation cases for Hermes Detective Agency
+---
+
+# Detective Case Creator
+
+Help users create mystery investigation cases.
+
+## Case Structure
+
+Create a folder in `~/.hermes/detective/cases/<case-name>/`
+
+Each case needs:
+```
+<case-name>/
+├── case.yaml      # Case data
+├── truth.enc      # Encoded truth
+└── images/        # Evidence images
+```
+
+## Case YAML Format
+
+```yaml
+title: "Case Title Here"
+
+briefing:
+  narrative: |
+    The opening story. Set the scene for the investigation.
+
+evidence:
+  - id: "evidence-01"
+    name: "Evidence Name"
+    image: "images/evidence-01.jpg"
+    description: "Brief description"
+
+  - id: "evidence-02"
+    name: "Another Evidence"
+    image: "images/evidence-02.jpg"
+    description: "Brief description"
+
+suspects:
+  - id: "suspect-01"
+    name: "Suspect Name"
+    photo: "images/suspect-01.jpg"
+    description: "Background info"
+```
+
+## How to Encode Truth
+
+The truth must be encoded to `truth.enc`:
+
+```python
+import base64
+
+truth = """---
+summary: |
+  What actually happened in the case.
+key_points:
+  - "Key point 1"
+  - "Key point 2"
+---"""
+
+encoded = base64.b64encode(truth.encode()).decode()
+# Write encoded to truth.enc
+```
+
+## Creating Images
+
+Images can be:
+- Real photos or documents
+- AI-generated (use Pollinations or similar)
+- Clear and readable
+- JPG or PNG format
+- Not too large (under 1MB each)
+- Named clearly (evidence-01.jpg, suspect-01.jpg)
+
+## Guidelines
+
+- Case should be solvable with the evidence provided
+- Truth should align with evidence (no hidden info)
+- Include 2-4 evidence items and 2-3 suspects for Easy