agentic-sx Phase 3: trace — console output as attached CID objects (TDD)

Per-agent buffer = persist append-only log stream + kv drain cursor;
commit-with-trace! drains everything-since-last-commit into a console-trace
object and binds it git-note style (ref notes/trace/<commit-cid> -> trace
cid). Trace never enters the commit tree; binding is a re-bindable ref layer
over immutable objects; failed commits keep the buffer; plain commit! leaves
binding to the agent. 35/35 (153/153 total).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/agentic/scoreboard.md

@@ -6,4 +6,5 @@ _Generated by `lib/agentic/conformance.sh`_
 |-------|-----:|-----:|------:|
 | schema | 65 | 0 | 65 |
 | branch | 53 | 0 | 53 |
-| **Total** | **118** | **0** | **118** |
+| trace | 35 | 0 | 35 |
+| **Total** | **153** | **0** | **153** |