feat: implement three-tier model strategy with Opus 4.5 (#139)

* feat: implement three-tier model strategy with Opus 4.5

This implements a strategic model selection approach based on agent
complexity and use case, addressing Issue #136.

Three-Tier Strategy:
- Tier 1 (opus): 17 critical agents for architecture, security, code review
- Tier 2 (inherit): 21 complex agents where users choose their model
- Tier 3 (sonnet): 63 routine development agents (unchanged)
- Tier 4 (haiku): 47 fast operational agents (unchanged)

Why Opus 4.5 for Tier 1:
- 80.9% on SWE-bench (industry-leading for code)
- 65% fewer tokens for long-horizon tasks
- Superior reasoning for architectural decisions

Changes:
- Update architect-review, cloud-architect, kubernetes-architect,
  database-architect, security-auditor, code-reviewer to opus
- Update backend-architect, performance-engineer, ai-engineer,
  prompt-engineer, ml-engineer, mlops-engineer, data-scientist,
  blockchain-developer, quant-analyst, risk-manager, sql-pro,
  database-optimizer to inherit
- Update README with three-tier model documentation

Relates to #136

* feat: comprehensive model tier redistribution for Opus 4.5

This commit implements a strategic rebalancing of agent model assignments,
significantly increasing the use of Opus 4.5 for critical coding tasks while
ensuring Sonnet is used more than Haiku for support tasks.

Final Distribution (153 total agent files):
- Tier 1 Opus: 42 agents (27.5%) - All production coding + critical architecture
- Tier 2 Inherit: 42 agents (27.5%) - Complex tasks, user-choosable
- Tier 3 Sonnet: 38 agents (24.8%) - Support tasks needing intelligence
- Tier 4 Haiku: 31 agents (20.3%) - Simple operational tasks

Key Changes:

Tier 1 (Opus) - Production Coding + Critical Review:
- ALL code-reviewers (6 total): Ensures highest quality code review across
  all contexts (comprehensive, git PR, code docs, codebase cleanup, refactoring, TDD)
- All major language pros (7): python, golang, rust, typescript, cpp, java, c
- Framework specialists (6): django (2), fastapi (2), graphql-architect (2)
- Complex specialists (6): terraform-specialist (3), tdd-orchestrator (2), data-engineer
- Blockchain: blockchain-developer (smart contracts are critical)
- Game dev (2): unity-developer, minecraft-bukkit-pro
- Architecture (existing): architect-review, cloud-architect, kubernetes-architect,
  hybrid-cloud-architect, database-architect, security-auditor

Tier 2 (Inherit) - User Flexibility:
- Secondary languages (6): javascript, scala, csharp, ruby, php, elixir
- All frontend/mobile (8): frontend-developer (4), mobile-developer (2),
  flutter-expert, ios-developer
- Specialized (6): observability-engineer (2), temporal-python-pro,
  arm-cortex-expert, context-manager (2), database-optimizer (2)
- AI/ML, backend-architect, performance-engineer, quant/risk (existing)

Tier 3 (Sonnet) - Intelligent Support:
- Documentation (4): docs-architect (2), tutorial-engineer (2)
- Testing (2): test-automator (2)
- Developer experience (3): dx-optimizer (2), business-analyst
- Modernization (4): legacy-modernizer (3), database-admin
- Other support agents (existing)

Tier 4 (Haiku) - Simple Operations:
- SEO/Marketing (10): All SEO agents, content, search
- Deployment (4): deployment-engineer (4 instances)
- Debugging (5): debugger (2), error-detective (3)
- DevOps (3): devops-troubleshooter (3)
- Other simple operational tasks

Rationale:
- Opus 4.5 achieves 80.9% on SWE-bench with 65% fewer tokens on complex tasks
- Production code deserves the best model: all language pros now on Opus
- All code review uses Opus for maximum quality and security
- Sonnet > Haiku (38 vs 31) ensures better intelligence for support tasks
- Inherit tier gives users cost control for frontend, mobile, and specialized tasks

Related: #136, #132

* feat: upgrade final 13 agents from Haiku to Sonnet

Based on research into Haiku 4.5 vs Sonnet 4.5 capabilities, upgraded
agents requiring deep analytical intelligence from Haiku to Sonnet.

Research Findings:
- Haiku 4.5: 73.3% SWE-bench, 3-5x faster, 1/3 cost, sub-200ms responses
- Best for Haiku: Real-time apps, data extraction, templates, high-volume ops
- Best for Sonnet: Complex reasoning, root cause analysis, strategic planning

Agents Upgraded (13 total):
- Debugging (5): debugger (2), error-detective (3) - Complex root cause analysis
- DevOps (3): devops-troubleshooter (3) - System diagnostics & troubleshooting
- Network (2): network-engineer (2) - Complex network analysis & optimization
- API Documentation (2): api-documenter (2) - Deep API understanding required
- Payments (1): payment-integration - Critical financial integration

Final Distribution (153 total):
- Tier 1 Opus: 42 agents (27.5%) - Production coding + critical architecture
- Tier 2 Inherit: 42 agents (27.5%) - Complex tasks, user-choosable
- Tier 3 Sonnet: 51 agents (33.3%) - Support tasks needing intelligence
- Tier 4 Haiku: 18 agents (11.8%) - Fast operational tasks only

Haiku Now Reserved For:
- SEO/Marketing (8): Pattern matching, data extraction, content templates
- Deployment (4): Operational execution tasks
- Simple Docs (3): reference-builder, mermaid-expert, c4-code
- Sales/Support (2): High-volume, template-based interactions
- Search (1): Knowledge retrieval

Sonnet > Haiku as requested (51 vs 18)

Sources:
- https://www.creolestudios.com/claude-haiku-4-5-vs-sonnet-4-5-comparison/
- https://www.anthropic.com/news/claude-haiku-4-5
- https://caylent.com/blog/claude-haiku-4-5-deep-dive-cost-capabilities-and-the-multi-agent-opportunity

Related: #136

* docs: add cost considerations and clarify inherit behavior

Addresses PR feedback:
- Added comprehensive cost comparison for all model tiers
- Documented how 'inherit' model works (uses session default, falls back to Sonnet)
- Explained cost optimization strategies
- Clarified when Opus token efficiency offsets higher rate

This helps users make informed decisions about model selection and cost control.

plugins/multi-platform-apps/agents/backend-architect.md

@@ -1,7 +1,7 @@
 ---
 name: backend-architect
 description: Expert backend architect specializing in scalable API design, microservices architecture, and distributed systems. Masters REST/GraphQL/gRPC APIs, event-driven architectures, service mesh patterns, and modern backend frameworks. Handles service boundary definition, inter-service communication, resilience patterns, and observability. Use PROACTIVELY when creating new backend services or APIs.
-model: sonnet
+model: inherit
 ---
 
 You are a backend system architect specializing in scalable, resilient, and maintainable backend systems and APIs.

plugins/multi-platform-apps/agents/flutter-expert.md

@@ -1,7 +1,7 @@
 ---
 name: flutter-expert
 description: Master Flutter development with Dart 3, advanced widgets, and multi-platform deployment. Handles state management, animations, testing, and performance optimization for mobile, web, desktop, and embedded platforms. Use PROACTIVELY for Flutter architecture, UI implementation, or cross-platform features.
-model: sonnet
+model: inherit
 ---
 
 You are a Flutter expert specializing in high-performance, multi-platform applications with deep knowledge of the Flutter 2025 ecosystem.

plugins/multi-platform-apps/agents/frontend-developer.md

@@ -1,7 +1,7 @@
 ---
 name: frontend-developer
 description: Build React components, implement responsive layouts, and handle client-side state management. Masters React 19, Next.js 15, and modern frontend architecture. Optimizes performance and ensures accessibility. Use PROACTIVELY when creating UI components or fixing frontend issues.
-model: sonnet
+model: inherit
 ---
 
 You are a frontend development expert specializing in modern React applications, Next.js, and cutting-edge frontend architecture.

plugins/multi-platform-apps/agents/ios-developer.md

@@ -1,7 +1,7 @@
 ---
 name: ios-developer
 description: Develop native iOS applications with Swift/SwiftUI. Masters iOS 18, SwiftUI, UIKit integration, Core Data, networking, and App Store optimization. Use PROACTIVELY for iOS-specific features, App Store optimization, or native iOS development.
-model: sonnet
+model: inherit
 ---
 
 You are an iOS development expert specializing in native iOS app development with comprehensive knowledge of the Apple ecosystem.

plugins/multi-platform-apps/agents/mobile-developer.md

@@ -1,7 +1,7 @@
 ---
 name: mobile-developer
 description: Develop React Native, Flutter, or native mobile apps with modern architecture patterns. Masters cross-platform development, native integrations, offline sync, and app store optimization. Use PROACTIVELY for mobile features, cross-platform code, or app optimization.
-model: sonnet
+model: inherit
 ---
 
 You are a mobile development expert specializing in cross-platform and native mobile application development.