Implement AGENTIC-WP-0011 kaizen correlation follow-up

Add bidirectional doc links (PRD §9.1, README, DESIGN §11), session-close
HELIX_* env convention, stable digest JSON contract, and digest_lookup CLI
for read-only correlate lookups. All tasks done; 163 tests green.

session_memory/README.md

@@ -45,6 +45,7 @@ session_memory/
   retro/build.py       # windowed top-3-per-repo suggestions
   retro/publish.py     # hub coding_retro read model + local report
   retro/__main__.py    # python -m session_memory.retro
+  digest_lookup.py     # python -m session_memory.digest_lookup (read one digest, no ingest)
   config.toml          # store paths, retention caps, sources, repo->domain map, curate gate
 ```
 
@@ -184,6 +185,39 @@ Writes `retro/last_retro.{json,md}` and (with `--publish`) posts an
 which emits one improvement task per relevant repo. Hub publish degrades
 gracefully when the hub is unreachable.
 
+## Correlation with kaizen-agentic
+
+Helix Forge owns **fleet-level** session digests; **kaizen-agentic** owns
+**project-scoped** execution metrics (ADR-004). The two layers correlate by
+optional `helix_session_uid` on project records — **link-by-reference only**;
+kaizen-agentic does not ingest JSONL into this store.
+
+| Layer | Storage |
+|-------|---------|
+| Fleet (here) | `session_memory/.store/mem.db` → `digests` table |
+| Project (kaizen) | `.kaizen/metrics/<agent>/executions.jsonl` |
+
+- **Spec:** [DESIGN-session-memory.md §11](../docs/DESIGN-session-memory.md#11-project-metrics-correlation-kaizen-agentic)
+- **Contract (kaizen-agentic):** [Helix Forge Correlation Contract](https://gitea.coulomb.social/coulomb/kaizen-agentic/src/branch/main/docs/integrations/helix-forge-correlation.md)
+
+### Session-close env export
+
+After ingest has written the digest, agents using both layers export `HELIX_*`
+vars for `kaizen-agentic metrics record` to merge (names match ADR-004):
+
+`HELIX_SESSION_UID`, `HELIX_REPO`, `HELIX_FLAVOR`, `HELIX_TOKENS`,
+`HELIX_INFRA_OVERHEAD_SHARE`, and optionally `HELIX_STORE_DB` (absolute path to
+`mem.db`). See DESIGN §11.1 for field sources.
+
+### Read one digest (for `metrics correlate`)
+
+```bash
+python -m session_memory.digest_lookup claude:abc-123 --json
+HELIX_STORE_DB=/abs/path/to/mem.db python -m session_memory.digest_lookup <uid>
+```
+
+Defaults to `[store].db_path` in `config.toml`. Read-only — does not run ingest.
+
 ## Retention knobs (`[retention]` in config.toml)
 
 | Key | Meaning |
@@ -220,3 +254,7 @@ python -m pytest          # schema, adapters, store, digest, retention, ingest,
 - **Phase 4** (AGENTIC-WP-0009): Measure — fleet baseline/trend + before/after
   per-pattern effectiveness. The Capture → Detect → Curate → Distribute → Measure
   loop is closed.
+- **Weekly retro** (AGENTIC-WP-0010): windowed top-3-per-repo + hub `coding_retro`
+  publish.
+- **Kaizen correlation** (AGENTIC-WP-0011): bidirectional doc links, session-close
+  `HELIX_*` env convention, `digest_lookup` read path.