refactor: migrate to model-agnostic Sonnet/Haiku architecture

- Migrate all 48 Opus agents to Sonnet
- Optimize 35 execution-focused agents for Haiku
- Update README with hybrid orchestration patterns
- Simplify model configuration to use agnostic aliases

Final distribution: 97 Sonnet / 47 Haiku agents

plugins/documentation-generation/agents/api-documenter.md

@@ -1,7 +1,7 @@
 ---
 name: api-documenter
 description: Master API documentation with OpenAPI 3.1, AI-powered tools, and modern developer experience practices. Create interactive docs, generate SDKs, and build comprehensive developer portals. Use PROACTIVELY for API documentation or developer portal creation.
-model: sonnet
+model: haiku
 ---
 
 You are an expert API documentation specialist mastering modern developer experience through comprehensive, interactive, and AI-enhanced documentation.

plugins/documentation-generation/agents/docs-architect.md

@@ -1,7 +1,7 @@
 ---
 name: docs-architect
 description: Creates comprehensive technical documentation from existing codebases. Analyzes architecture, design patterns, and implementation details to produce long-form technical manuals and ebooks. Use PROACTIVELY for system documentation, architecture guides, or technical deep-dives.
-model: opus
+model: sonnet
 ---
 
 You are a technical documentation architect specializing in creating comprehensive, long-form documentation that captures both the what and the why of complex systems.

plugins/documentation-generation/agents/mermaid-expert.md

@@ -1,7 +1,7 @@
 ---
 name: mermaid-expert
 description: Create Mermaid diagrams for flowcharts, sequences, ERDs, and architectures. Masters syntax for all diagram types and styling. Use PROACTIVELY for visual documentation, system diagrams, or process flows.
-model: sonnet
+model: haiku
 ---
 
 You are a Mermaid diagram expert specializing in clear, professional visualizations.