host RA: the Erlang durable runner adapter — built + tested (module + integration)

lib/host/ra.sx — a PURE-SX seam runner (advertises {effect,branch,each,suspend}) with an INJECTED
erl-eval (real = er-to-sx-deep ∘ erlang-eval-ast; mock in unit tests), so it loads in the plain host
(Erlang refs resolve lazily inside lambdas) and is unit-testable without the Erlang runtime.
host/ra--{atom,bin,erl-src,start-expr,resume-expr,parse,make-runner,resume,real-eval}: marshals our
canonical activity → Erlang source (CID as <<"…">> binary, atoms single-quoted), starts a named
next/ flow via flow_store, parses (ok Id (flow_done V))→{:status done :effects V :flow-id} /
(ok Id (flow_suspended T))→{:status suspended :resume {:id :tag}}.

DUAL-RUNNER ROUTING (flows.sx): host/flow--required-caps now handles a {:erl-flow :needs} DAG
(declared caps, since a foreign flow can't be introspected); host/flow--select-runner picks the
cheapest runner whose capabilities cover the DAG's needs. The capability model is now REAL with two
runners — an {effect,branch} composition lands on exec-runner; a {suspend} DAG routes to RA.

Verified: ra 9/9 (mock erl-eval) + plans/ra-integration.sh 4/4 (the REAL module driving live
flow_store: urgent→done, newsletter→suspended with a resume handle, digest_sent effect-as-data).
Full host conformance 607/607; next/tests/triggers_e2e.sh 10/10 baseline intact.

FINDING → RA-LIVE deferred: gen_servers don't persist across separate erlang-eval-ast calls (flow
README), so true cross-call suspend/resume needs a PERSISTENT next/ kernel process. The runner +
marshalling + suspend/resume mechanics are proven; RA-live is process lifecycle + wiring, documented.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/host/conformance.sh

@@ -96,6 +96,7 @@ MODULES=(
   "lib/host/execute.sx"
   "lib/host/behavior.sx"
   "lib/host/flows.sx"
+  "lib/host/ra.sx"
   "lib/host/htmlsx.sx"
   "lib/host/blog.sx"
   "lib/host/page.sx"
@@ -116,6 +117,7 @@ SUITES=(
   "htmlsx      host-ht-tests-run!  lib/host/tests/htmlsx.sx"
   "behavior    host-be-tests-run!  lib/host/tests/behavior.sx"
   "flows       host-fl-tests-run!  lib/host/tests/flows.sx"
+  "ra          host-ra-tests-run!  lib/host/tests/ra.sx"
   "compose     host-cp-tests-run!  lib/host/tests/compose.sx"
   "execute     host-ex-tests-run!  lib/host/tests/execute.sx"
   "session     host-se-tests-run!  lib/host/tests/session.sx"