feat: Add comprehensive architecture documentation

[buremba]

Create detailed ARCHITECTURE.md with system overview and technical implementation details

• Include mermaid diagrams showing system architecture, data flow, and session lifecycle
• Document dispatcher-worker pattern with Kubernetes job management
• Explain thread-based session management and workspace isolation
• Cover current Kubernetes implementation and future Docker-in-Docker plans
• Detail security, monitoring, and deployment patterns

Fixes #10

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PR Review: Architecture Documentation

Todo List:

• Read and analyze ARCHITECTURE.md content
• Review documentation structure and organization
• Evaluate technical accuracy and completeness
• Check mermaid diagram quality and clarity
• Assess security and deployment documentation
• Provide comprehensive review feedback

Review Feedback

This is an excellent comprehensive architecture document that provides deep technical insight into the Claude Code Slack integration system. The documentation is well-structured, technically accurate, and provides great value for developers and system administrators.

✅ Strengths

Documentation Quality:

• Excellent Organization: Clear hierarchical structure from high-level overview to implementation details
• Visual Excellence: Mermaid diagrams effectively illustrate system architecture, data flows, and state transitions
• Complete Coverage: Covers all major system components, patterns, and operational aspects
• Technical Depth: Provides both conceptual understanding and implementation specifics

Technical Accuracy:

• Accurate System Description: Correctly describes dispatcher-worker pattern with Kubernetes jobs
• Detailed Component Analysis: Comprehensive coverage of dispatcher, worker, and core-runner roles
• Realistic Resource Specifications: CPU/memory allocations and timeouts match production requirements
• Security Considerations: Well-documented isolation, RBAC, and secrets management

Architectural Insights:

• Thread-as-Session Concept: Innovative approach to persistent conversation context
• Resource Management: Smart ephemeral worker pattern with proper cleanup
• Scalability Design: Clear horizontal scaling characteristics and performance metrics

🎯 Key Highlights

1. System Architecture Diagram (lines 11-53): Outstanding visual representation showing the relationship between Slack, Kubernetes, and external services with proper component classification

2. Sequence Diagram (lines 102-133): Excellent illustration of the complete message processing flow from Slack mention to final response

3. Session Lifecycle (lines 152-163): Clear state diagram showing how threads maintain continuity across interactions

4. Security Section (lines 365-398): Comprehensive coverage of multi-tenant isolation, secrets management, and access control

📋 Minor Suggestions for Enhancement

Code References:

• Consider adding line number ranges for the referenced files (e.g., packages/dispatcher/src/kubernetes/job-manager.ts:259-276)
• Some file references could include brief descriptions of key functions/classes

Technical Completeness:

• Error Handling: Could add a section on error handling patterns and recovery mechanisms
• Backup/Recovery: Brief mention of conversation history backup strategies
• Network Policies: Kubernetes network policies for enhanced pod-to-pod isolation could be mentioned

Operational Details:

• Debugging Guide: A troubleshooting section for common deployment and runtime issues
• Cost Analysis: Rough cost estimates for different usage patterns would be valuable
• Capacity Planning: Guidelines for sizing clusters based on expected concurrent users

🔧 Very Minor Technical Notes

1. Line 172: Session key format could include an example for clarity
2. Lines 227-244: Resource specifications are repeated - could reference the original values.yaml
3. Line 476: "~100 concurrent sessions per cluster" - this seems conservative and could note it's configurable

📊 Code Quality Assessment

• Structure: ⭐⭐⭐⭐⭐ Excellent organization and flow
• Clarity: ⭐⭐⭐⭐⭐ Clear explanations accessible to different technical levels
• Completeness: ⭐⭐⭐⭐⭐ Comprehensive coverage of all system aspects
• Visual Design: ⭐⭐⭐⭐⭐ Outstanding use of diagrams and formatting
• Technical Accuracy: ⭐⭐⭐⭐⭐ Matches codebase implementation accurately

🚀 Overall Assessment

This documentation represents a gold standard for technical architecture documentation. It successfully bridges the gap between high-level system understanding and implementation details. The combination of narrative explanations, visual diagrams, and code examples creates an excellent resource for:

• Developers: Understanding system components and integration points
• DevOps Engineers: Deployment, monitoring, and operational procedures
• Architects: System design patterns and scalability characteristics
• Security Teams: Isolation mechanisms and access controls

Recommendation: ✅ Approve - This PR significantly enhances the project's documentation and provides immense value for current and future contributors.

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