feat: add comprehensive architecture documentation

- Add AGENT-ONBOARDING.md for AI agents
- Add ARCHITECTURE.md with full system overview
- Add TECH-STACK.md with complete technology inventory
- Add DOMAIN-MODEL.md with entities and bounded contexts
- Add CODING-CONVENTIONS.md with patterns and practices
- Add GLOSSARY.md with terminology reference
- Add C4 diagrams (Context and Container levels)
- Add 10 ADRs documenting key decisions:
  - Talos Linux, NATS, MessagePack, Multi-GPU strategy
  - GitOps with Flux, KServe, Milvus, Dual workflow engines
  - Envoy Gateway
- Add specs directory with JetStream configuration
- Add diagrams for GPU allocation and data flows

Based on analysis of homelab-k8s2 and llm-workflows repositories
and kubectl cluster-info dump data.

specs/README.md

@@ -0,0 +1,36 @@
+# Specifications
+
+This directory contains feature-level specifications and technical designs.
+
+## Contents
+
+- [BINARY_MESSAGES_AND_JETSTREAM.md](BINARY_MESSAGES_AND_JETSTREAM.md) - MessagePack format and JetStream configuration
+- Future specs will be added here
+
+## Spec Template
+
+```markdown
+# Feature Name
+
+## Overview
+Brief description of the feature
+
+## Requirements
+- Requirement 1
+- Requirement 2
+
+## Design
+Technical design details
+
+## API
+Interface definitions
+
+## Implementation Notes
+Key implementation considerations
+
+## Testing
+Test strategy
+
+## Open Questions
+Unresolved items
+```