Summary

The architect schema for ACON compression guidelines included conversation_id INTEGER REFERENCES conversations(id) ON DELETE CASCADE for per-conversation scoping. This was omitted in the implementation (crates/zeph-memory/migrations/032_compression_guidelines.sql).

Adding this column later requires ALTER TABLE ADD COLUMN and a new migration.

Fix

Add a new migration that adds the conversation_id column (nullable, no NOT NULL constraint for backwards compatibility with existing rows), and update the query logic to scope guidelines per conversation when set.

Acceptable simplification for MVP, but needed for per-conversation guidelines support.

Identified by code reviewer (REVIEW-11) during ACON compression guidelines PR (#1647) review.