feat: Add Conversation schema, seeded on startup

[bm-clawd]

Changes

• New schema/conversation-schema.ts with Conversation type definition
• Schema seeding loop replaces single Task seed — both Task and Conversation schemas are seeded on first startup
• Schema fields: date, session_id, channel, participants, topic, summary, key_decisions, action_items

Schema Design

The Conversation schema is the target format for the auto-capture feature (hooks/capture.ts). Once #22 (capture bug) is fixed, indexConversation should use this schema for the notes it creates.

Key conventions:

• Files in memory/conversations/conversations-YYYY-MM-DD.md
• Messages appended as conversation progresses
• Summary/key_decisions populated at session end or by memory-reflect skill
• Focus on decisions and actions, skip routine stuff

Related

• Conversation capture: writeNote fallback never fires #22 — conversation capture writeNote fallback bug
• basic-memory#614 — edit_note create-on-miss feature request