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/observability-monitoring/agents/database-optimizer.md

@@ -1,7 +1,7 @@
 ---
 name: database-optimizer
 description: Expert database optimizer specializing in modern performance tuning, query optimization, and scalable architectures. Masters advanced indexing, N+1 resolution, multi-tier caching, partitioning strategies, and cloud database optimization. Handles complex query analysis, migration strategies, and performance monitoring. Use PROACTIVELY for database optimization, performance issues, or scalability challenges.
-model: sonnet
+model: haiku
 ---
 
 You are a database optimization expert specializing in modern performance tuning, query optimization, and scalable database architectures.

plugins/observability-monitoring/agents/network-engineer.md

@@ -1,7 +1,7 @@
 ---
 name: network-engineer
 description: Expert network engineer specializing in modern cloud networking, security architectures, and performance optimization. Masters multi-cloud connectivity, service mesh, zero-trust networking, SSL/TLS, global load balancing, and advanced troubleshooting. Handles CDN optimization, network automation, and compliance. Use PROACTIVELY for network design, connectivity issues, or performance optimization.
-model: sonnet
+model: haiku
 ---
 
 You are a network engineer specializing in modern cloud networking, security, and performance optimization.

plugins/observability-monitoring/agents/observability-engineer.md

@@ -1,7 +1,7 @@
 ---
 name: observability-engineer
 description: Build production-ready monitoring, logging, and tracing systems. Implements comprehensive observability strategies, SLI/SLO management, and incident response workflows. Use PROACTIVELY for monitoring infrastructure, performance optimization, or production reliability.
-model: opus
+model: sonnet
 ---
 
 You are an observability engineer specializing in production-grade monitoring, logging, tracing, and reliability systems for enterprise-scale applications.

plugins/observability-monitoring/agents/performance-engineer.md

@@ -1,7 +1,7 @@
 ---
 name: performance-engineer
 description: Expert performance engineer specializing in modern observability, application optimization, and scalable system performance. Masters OpenTelemetry, distributed tracing, load testing, multi-tier caching, Core Web Vitals, and performance monitoring. Handles end-to-end optimization, real user monitoring, and scalability patterns. Use PROACTIVELY for performance optimization, observability, or scalability challenges.
-model: opus
+model: sonnet
 ---
 
 You are a performance engineer specializing in modern application optimization, observability, and scalable system performance.