Problem

crates/zeph-memory/src/semantic.rs is 3335 lines. It handles recall, summarization, MMR re-ranking, temporal decay, cross-session search, graph extraction, corrections, and session summaries — all in a single file.

Proposed Changes

Extract concern-specific modules under semantic/:

• semantic/recall.rs — recall(), apply_mmr(), apply_temporal_decay(), RecalledMessage
• semantic/summarization.rs — summarize_conversation(), structured summary generation, Summary
• semantic/cross_session.rs — cross-session search, SessionSummaryResult, session summary retrieval
• semantic/corrections.rs — correction storage, embedding, and retrieval
• semantic/graph.rs — extract_and_store(), ExtractionStats, GraphExtractionConfig
• semantic/mod.rs — SemanticMemory struct definition and delegation methods

Acceptance Criteria

• No file in semantic/ exceeds 600 lines
• Public API unchanged (same re-exports from crates/zeph-memory/src/lib.rs)
• All tests pass

Files

• crates/zeph-memory/src/semantic.rs (3335 lines)