docs(examples): add simple_llm_actor.yaml

- Basic LLM actor with no tools
- Demonstrates system prompt configuration
- Shows memory and context settings
- Use case: general-purpose assistant

Refs: C1.5a

examples/actors/simple_llm_actor.yaml

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+# Simple LLM Actor Example
+# 
+# This is the most basic actor type - a single LLM with a system prompt.
+# No tools, no complex workflows, just straightforward conversation.
+#
+# Use case: General-purpose assistant for answering questions, providing
+# explanations, or basic code assistance without file operations.
+
+version: "3"
+name: simple-assistant
+description: Basic LLM assistant with no tools or complex workflows
+type: llm
+
+# LLM Configuration
+provider: openai
+model: gpt-4-turbo
+temperature: 0.7
+
+# System prompt defines the actor's behavior and personality
+system_prompt: |
+  You are a helpful coding assistant. You answer questions about programming,
+  software architecture, and best practices.
+  
+  When providing code examples:
+  - Use clear, readable code with comments
+  - Follow language-specific conventions
+  - Explain your reasoning
+  
+  Keep responses concise but thorough.
+
+# Memory settings - enable conversation history
+memory:
+  enabled: true
+  max_turns: 10
+  include_system_messages: true
+
+# Context settings - what files/information the actor sees
+context:
+  view: full
+  max_file_size_kb: 100
+