Phase 2: Add Context ID support and AI-native message format

[bokelley]

Overview

Implement Phase 2 enhancements for AdCP specification compatibility.

Tasks

Context ID Support

• Add context ID generation for discovery sessions (ctx_<timestamp>_<random>)
• Store discovery context with signal IDs and search parameters
• Link activations back to their discovery context
• Implement 7-day expiration for context storage (to support 72-hour activation windows)
• Update client to display and use context IDs

AI-Native Message Format (PR #21)

• Add universal message field as first field in all responses
• Generate human-readable summaries for all responses
• Add optional clarification_needed field
• Update client to prominently display message field

Benefits

• Workflow tracking from discovery to activation
• Better debugging and analytics
• AI-friendly responses for LLM consumption
• Preparation for A2A protocol support

Acceptance Criteria

• Context IDs properly link discovery and activation workflows
• All responses include meaningful message summaries
• Client displays messages prominently
• Context IDs persist for 7 days

References

• AdCP PR Introduce Apache 2.0 LICENSE and CONTRIBUTING.md #21: AI-native message format
• Context IDs prepare for A2A protocol which requires contextId