add c4 documentation workflow and agents (#129)

* add c4 documentation workflow and agents

* update the c4-code agent to use proper mermaid diagram types

docs/usage.md

@@ -120,6 +120,7 @@ Claude Code automatically selects and coordinates the appropriate agents based o
 | `/code-documentation:doc-generate` | Generate comprehensive documentation |
 | `/code-documentation:code-explain` | Explain code functionality |
 | `/documentation-generation:doc-generate` | OpenAPI specs, diagrams, tutorials |
+| `/c4-architecture:c4-architecture` | Generate comprehensive C4 architecture documentation (Context, Container, Component, Code) |
 
 ### Refactoring & Maintenance
 
@@ -262,6 +263,27 @@ Plugins provide pre-configured multi-agent workflows accessible via slash comman
 
 **Orchestration:** incident-responder → devops-troubleshooter → debugger → error-detective → observability-engineer
 
+### C4 Architecture Documentation
+
+```bash
+# Generate comprehensive C4 architecture documentation
+/c4-architecture:c4-architecture
+
+# Natural language alternative
+"Create C4 architecture documentation for this codebase"
+```
+
+**Orchestration:** c4-code → c4-component → c4-container → c4-context
+
+**What happens:**
+
+1. **Code Level**: Bottom-up analysis of all subdirectories, creating code-level documentation with function signatures and dependencies
+2. **Component Level**: Synthesizes code documentation into logical components with interfaces and relationships
+3. **Container Level**: Maps components to deployment containers with OpenAPI/Swagger API specifications
+4. **Context Level**: Creates high-level system context with personas, user journeys, and external dependencies
+
+**Output:** Complete C4 documentation in `C4-Documentation/` directory with Mermaid diagrams at all levels (Context, Container, Component, Code)
+
 ## Command Arguments and Options
 
 Many slash commands support arguments for precise control:
@@ -289,6 +311,9 @@ Many slash commands support arguments for precise control:
 
 # Python project scaffolding
 /python-development:python-scaffold fastapi-microservice
+
+# C4 architecture documentation generation
+/c4-architecture:c4-architecture
 ```
 
 ## Combining Natural Language and Commands
@@ -367,5 +392,5 @@ See [Agent Skills](./agent-skills.md) for details on the 47 specialized skills.
 
 - [Agent Skills](./agent-skills.md) - Specialized knowledge packages
 - [Agent Reference](./agents.md) - Complete agent catalog
-- [Plugin Reference](./plugins.md) - All 63 plugins
+- [Plugin Reference](./plugins.md) - All 65 plugins
 - [Architecture](./architecture.md) - Design principles