Enhance multi-instance documentation with diagrams and examples

[freema]

Summary

This PR significantly improves the documentation for OpenClaw's multi-instance mode by adding visual architecture diagrams, practical usage examples, and clearer configuration guidance. The changes make it easier for users to understand how to set up and use multiple gateway instances.

Key Changes

• Added architecture diagrams in both README.md and docs/configuration.md to visualize the multi-instance topology and request routing flow
• Expanded usage examples with concrete CLI examples showing how to target specific instances (prod, staging, dev)
• Clarified instance resolution logic with step-by-step explanation of how the system selects which instance to use
• Added Docker Compose example demonstrating multi-instance configuration in a containerized environment
• Reorganized README section with new subsections (Setup, Usage, Key Features) for better readability
• Enhanced feature highlights including zero-migration upgrade path, per-instance isolation, dynamic routing, and security notes
• Improved backward compatibility messaging to emphasize that existing single-instance deployments require no changes

Notable Details

• Documentation now includes visual ASCII diagrams showing the complete request flow from Claude client through the MCP bridge to multiple OpenClaw gateways
• Examples demonstrate all major tools (openclaw_chat, openclaw_status, openclaw_instances, openclaw_chat_async, openclaw_task_list) with instance parameters
• Configuration documentation clarifies that tokens are never exposed via the openclaw_instances tool for security
• Added explicit note that async tasks store target instance ID for correct result routing

https://claude.ai/code/session_01XU8X5UK1Pq6jy78RTy18jG