Add IT-One AI agent template, eval gate, and deployment skeleton

docs/system-architecture.md

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+# System architecture
+
+```mermaid
+flowchart LR
+  Input[User request] --> Core[Agent graph]
+  Core --> Prompt[Versioned prompts]
+  Core --> Tools[External tools]
+  Core --> Memory[Memory / RAG]
+  Core --> Output[Validated response]
+  Evals[Offline evals] --> Gate[PR quality gate]
+  Gate --> Core
+```
+
+The core must keep orchestration deterministic enough to test. Tools should have explicit schemas and timeouts. Memory adapters must make retention and deletion behavior visible.