fix: preserve memory relationships through recall

[cucupac]

What Changed

Recall preserves the recorded relationships between retrieved memories. Fast-mode and fallback briefs keep selected memory order without repeating linked solutions.

Why

Retrieval used these relationships to find memories but discarded them before synthesis, leaving the agent to infer which outcome belonged to which situation.

How

• Carry deduplicated memory_relations and their lifecycle metadata through the shared evidence pack, internal reads, and synthesis.
• Include a relation only when both endpoints are selected and visible.
• Render connected cases in prior_cases and raise an error when the relationship field is missing.
• Reuse existing tables and queries, keeping retrieval ranking and limits unchanged.