Add documentation for the dynamicAgentCreation feature used to create
isolated agents per Feishu/Lark user. Covers:
- dynamicAgentCreation configuration fields (enabled, workspaceTemplate,
agentDirTemplate, maxAgents)
- Automatic agent/workspace creation flow
- Session isolation with dmScope
- Template variables ({agentId}, {userId})
- Verification steps and example deployment
Refs: feature available since OpenClaw 2026.4.25+
Co-authored-by: li <li@lideMac-mini.local>
d012065ecf
