RFC 0013: Agent Sandbox Showcase

[dligthart]

Implement the Agent Sandbox Showcase to demonstrate WordClaw's differentiators through a scenario-based architecture as outlined in doc/rfc/partially-implemented/0013-agent-sandbox-showcase.md

[dligthart]

Reviewed RFC 0013 implementation against current code. Opened follow-up implementation gaps:

• RFC 0013 gap: Persist and deep-link guided scenario progress #113 RFC 0013 gap: Persist and deep-link guided scenario progress
• RFC 0013 gap: Add replay-current-step control in Guided Scenarios #114 RFC 0013 gap: Add replay-current-step control in Guided Scenarios
• RFC 0013 gap: Tri-protocol showcase is missing an executable MCP step #115 RFC 0013 gap: Tri-protocol showcase is missing an executable MCP step
• RFC 0013 gap: Guided scenarios rely on brittle hardcoded IDs and tenant assumptions #116 RFC 0013 gap: Guided scenarios rely on brittle hardcoded IDs and tenant assumptions

These are scoped as incremental tasks to complete RFC 0013 behavior and demo reliability.