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.

docs/PRD-helix-forge.md

@@ -5,7 +5,7 @@
 **Status:** Draft v0.1
 **Author:** Claude (drafted with Bernd Worsch)
 **Created:** 2026-06-06
-**Updated:** 2026-06-06
+**Updated:** 2026-06-19
 
 ---
 
@@ -223,6 +223,32 @@ record:
 - The hub remains a **read model**; Helix Forge writes its durable artifacts as files
   and lets the hub index them.
 
+### 9.1 Downstream: kaizen-agentic project metrics correlation
+
+Helix Forge is a **fleet-level** producer of normalized session digests. The
+**kaizen-agentic** framework is a **project-scoped** consumer of optional
+correlation fields on its execution metrics (ADR-004). The two layers link
+**by reference** — kaizen-agentic does not re-implement JSONL ingestion or write
+into the Helix Forge store.
+
+| Layer | Owner | What it stores |
+|-------|-------|----------------|
+| Fleet | agentic-resources (`session_memory`) | Per-session digests in the local SQLite store |
+| Project | kaizen-agentic | `.kaizen/metrics/<agent>/executions.jsonl` |
+
+**Canonical spec in this repo:** [DESIGN-session-memory.md §11](DESIGN-session-memory.md#11-project-metrics-correlation-kaizen-agentic)
+(session-close env export, digest read path, stable JSON shape).
+
+**Authoritative cross-repo contract (kaizen-agentic):**
+[Helix Forge Correlation Contract](https://gitea.coulomb.social/coulomb/kaizen-agentic/src/branch/main/docs/integrations/helix-forge-correlation.md).
+Field mapping: `Session.session_uid` → `helix_session_uid`; digest token totals →
+`tokens`; MCP/tool overhead share → `infra_overhead_share`.
+
+**Read path for consumers:** `HELIX_STORE_DB` points at the digest SQLite file
+(default `session_memory/.store/mem.db`); `python -m session_memory.digest_lookup
+<uid> --json` or `kaizen-agentic metrics correlate <uid>` performs a read-only
+lookup. No ingestion code belongs in kaizen-agentic.
+
 ## 10. Success Metrics
 
 | Metric | Meaning | Target (directional, v1) |