swarm: document local-swarm harness + one-flip seam in README

lang/swarm/README.md

@@ -91,6 +91,28 @@ source <sandbox>/.nsbx-env
 lang/swarm/build.sh lang/swarm/tests/integ_engram.el /tmp/i && /tmp/i
 ```
 
+## Local-swarm integration harness (the one flip)
+
+`tests/harness_local_swarm.el` proves the **full local-swarm mechanics today** on
+the isolated clone with the primitive seam pointed at the hermetic stub — 17/17
+green: 8 native-thread workers at concurrency 4, reduce + vote convergence, CCR
+scoping + non-leak, all three containment rules (incl. live Rule-2 denial),
+durable work-tracking, and **afferent telemetry** observed by the @manager.
+
+Binding to the reshape's decorated primitives is **one flip and a run**:
+
+```
+# in primitive_binding.el — change one line each:
+fn bound_think(ctx, instruction) { return think(ctx, instruction) }   # decorated, dharma bus
+# then:
+SWARM_PRIMITIVE_SEAM=decorated  lang/swarm/build.sh tests/harness_local_swarm.el ./h && ./h
+```
+
+Nothing else in the swarm changes. `primitive_seam.el` (`seam_think/attend/learn`)
+already routes every worker primitive call through this one switch, and the same
+harness runs the bound path. Today `SWARM_PRIMITIVE_SEAM=decorated` still runs
+green because the binding falls back to the stub — proving the flip path executes.
+
 ## Built vs stubbed (honest)
 
 **Real, tested:**