Implement conversational mesh edge services from merged standards

[mdheller]

Implement the runtime-side conversational mesh edge in prophet-platform based on the newly merged standards in socioprophet-standards-storage.

Scope:

• Matrix-native edge service
• external channel adapter ingress
• canonical ConversationEnvelope normalization
• trust-tier and fragility-tier tagging
• internal vs external room separation
• bridge health monitoring

Acceptance criteria:

• runtime app or service layout exists in prophet-platform
• canonical conversational schemas are consumed from standards-storage
• at least one native path and one adapter path emit canonical ConversationEnvelope records
• health and operator-facing status are observable
• validate and smoke checks remain green