klieo-memory-graph 3.4.0

# klieo-memory-graph

`KnowledgeGraph` trait surface + `InMemoryGraph` for klieo GraphRAG.

**Status:** stable at 3.x. Trait freeze contract recorded in [ADR-039](../../docs/adr/adr-039-graphrag-1-0-promotion.md).

## Production wiring

This crate is the **trait surface only**. For production deployments
plug a real backend:

- [`klieo-memory-graph-neo4j`](https://crates.io/crates/klieo-memory-graph-neo4j) —
  Neo4j-backed `Neo4jKnowledgeGraph` (recommended for multi-process
  agent fleets). See that crate's README for the
  `MemoryNeo4j → Neo4jKnowledgeGraph` wiring.

`InMemoryGraph` (this crate) is petgraph-backed and intended for unit
tests and the M1 spike only — not for shipping agents.

## Cargo features

| Feature | Default | Purpose |
|---|---|---|
| `provenance` | **on** | Surfaces `klieo_provenance::ChainEntry` on `PathHop::chain_entry`. Graph-only consumers can disable via `default-features = false` to drop the audit-chain stack (`ed25519-dalek`, `sha2`, `hex`). |

## Layers

- `klieo-core` (Layer 0) — frozen
- **`klieo-memory-graph`** (Layer 1) — this crate
- `klieo-memory-graph-neo4j` (Layer 2, separate crate) — Neo4j backend
- `klieo-memory-graph-rag` (Layer 2, separate crate) — composer

## What lives here

- `KnowledgeGraph` trait (M1) — retrieval (`neighbors`/`recall_paths`/
  `recall_filtered`) plus `subgraph(scope, limit)` for bounded whole-graph
  enumeration (backs the ops-viz explorer)
- `GraphView` / `GraphNode` / `GraphEdge` — the browsable subgraph snapshot;
  `GraphView::fact_texts` is a sidecar mapping fact ids to their sentence text
- `FilterableLongTermMemory` supertrait of `LongTermMemory` (M1)
- `EntityExtractor` trait (M1)
- `EntityType` / `EntityRef` / `known_epoch()` (M1)
- `InMemoryGraph` — petgraph `StableGraph` impl for tests + spike only (M1)
- `RecallMetrics` — hit@k + projector-lag counters (M1)

## License

MIT.