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.

decisions/0004-use-messagepack-for-nats.md

@@ -0,0 +1,137 @@
+# Use MessagePack for NATS Messages
+
+* Status: accepted
+* Date: 2025-12-01
+* Deciders: Billy Davies
+* Technical Story: Selecting serialization format for NATS messages
+
+## Context and Problem Statement
+
+NATS messages in the AI platform carry various payloads:
+- Text chat messages (small)
+- Voice audio data (potentially large, base64 or binary)
+- Streaming response chunks
+- Pipeline parameters
+
+We need a serialization format that handles both text and binary efficiently.
+
+## Decision Drivers
+
+* Efficient binary data handling (audio)
+* Compact message size
+* Fast serialization/deserialization
+* Cross-language support (Python, Go)
+* Debugging ability
+* Schema flexibility
+
+## Considered Options
+
+* JSON
+* Protocol Buffers (protobuf)
+* MessagePack (msgpack)
+* CBOR
+* Avro
+
+## Decision Outcome
+
+Chosen option: "MessagePack (msgpack)", because it provides binary efficiency with JSON-like simplicity and schema-less flexibility.
+
+### Positive Consequences
+
+* Native binary support (no base64 overhead for audio)
+* 20-50% smaller than JSON for typical messages
+* Faster serialization than JSON
+* No schema compilation step
+* Easy debugging (can pretty-print like JSON)
+* Excellent Python and Go libraries
+
+### Negative Consequences
+
+* Less human-readable than JSON when raw
+* No built-in schema validation
+* Slightly less common than JSON
+
+## Pros and Cons of the Options
+
+### JSON
+
+* Good, because human-readable
+* Good, because universal support
+* Good, because no setup required
+* Bad, because binary data requires base64 (33% overhead)
+* Bad, because larger message sizes
+* Bad, because slower parsing
+
+### Protocol Buffers
+
+* Good, because very compact
+* Good, because fast
+* Good, because schema validation
+* Good, because cross-language
+* Bad, because requires schema definition
+* Bad, because compilation step
+* Bad, because less flexible for evolving schemas
+* Bad, because overkill for simple messages
+
+### MessagePack
+
+* Good, because binary-efficient
+* Good, because JSON-like simplicity
+* Good, because no schema required
+* Good, because excellent library support
+* Good, because can include raw bytes
+* Bad, because not human-readable raw
+* Bad, because no schema validation
+
+### CBOR
+
+* Good, because binary-efficient
+* Good, because IETF standard
+* Good, because schema-less
+* Bad, because less common libraries
+* Bad, because smaller community
+* Bad, because similar to msgpack with less adoption
+
+### Avro
+
+* Good, because schema evolution
+* Good, because compact
+* Good, because schema registry integration
+* Bad, because requires schema
+* Bad, because more complex setup
+* Bad, because Java-centric ecosystem
+
+## Implementation Notes
+
+```python
+# Python usage
+import msgpack
+
+# Serialize
+data = {
+    "user_id": "user-123",
+    "audio": audio_bytes,  # Raw bytes, no base64
+    "premium": True
+}
+payload = msgpack.packb(data)
+
+# Deserialize
+data = msgpack.unpackb(payload, raw=False)
+```
+
+```go
+// Go usage
+import "github.com/vmihailenco/msgpack/v5"
+
+type Message struct {
+    UserID string `msgpack:"user_id"`
+    Audio  []byte `msgpack:"audio"`
+}
+```
+
+## Links
+
+* [MessagePack Specification](https://msgpack.org)
+* [msgpack-python](https://github.com/msgpack/msgpack-python)
+* Related: [ADR-0003](0003-use-nats-for-messaging.md) - Message bus choice
+* See: [BINARY_MESSAGES_AND_JETSTREAM.md](../specs/BINARY_MESSAGES_AND_JETSTREAM.md)