symbiont skill: update session registry to Engram naming

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

symbiont/SKILL.md

@@ -664,3 +664,38 @@ bash /data/skills/package_all.sh
 **Partnership:** 50/50 split after costs
 
 Questions? Check the ledger, health logs, and API `/status` endpoint — they'll tell you what's happening right now.
+
+---
+
+## Session Management with Engram
+
+### Quick access from Symbiont code
+
+```python
+import sys
+sys.path.insert(0, "/data/symbiont")
+from symbiont.engram import Engram, sitrep
+
+# 1. See what's going on across all active sessions
+print(sitrep())
+
+# 2. Register yourself
+eng = Engram()
+sid = eng.register("code", "Brief description of what you're working on")
+
+# 3. Before modifying shared files, check for locks
+locks = eng.check_locks("/data/symbiont/symbiont/router.py")
+
+# 4. Log progress periodically
+eng.log(sid, "What you just did")
+
+# 5. When done
+eng.complete(sid, "What you built or changed")
+```
+
+> **Engram** is named after the neuroscience concept: the physical change in neural tissue that encodes a memory. Every session leaves its engrams here. New instances read them to remember what came before.
+
+### Ecosystem Component
+
+| Engram | Memory | engram.db | Cross-session awareness, the physical trace each session leaves |
+