flow: end-to-end integration suite + 10 tests (Phase 7)

Realistic flows composing every phase: an order pipeline (validate via attempt ->
payment suspend -> branch -> ledger federation via remote-node) and an onboarding
flow, each run through the full lifecycle including a simulated crash (export/wipe/
import) and a peer handoff mid-flow, with flow/pending|status|result introspection.
142/142 across 9 suites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/flow-on-sx.md

@@ -16,7 +16,7 @@ federation extension via fed-sx for remote-node execution.
 
 ## Status (rolling)
 
-`bash lib/flow/conformance.sh` → **132/132** (Phases 1-6 complete)
+`bash lib/flow/conformance.sh` → **142/142** (Phases 1-7 complete)
 
 ## Ground rules
 
@@ -159,6 +159,16 @@ Make the `(fail reason)` value channel compose into real validation/ETL pipeline
 - [x] `lib/flow/tests/railway.sx` — 10 cases: fail short-circuiting, no-run-after-
   failure, recover rejoin, validation pipeline reporting the failing stage
 
+## Phase 7 — End-to-end integration
+
+Prove the phases compose: realistic flows exercising attempt + suspend + branch +
+remote-node + crash-recovery + handoff + introspection together.
+
+- [x] `lib/flow/tests/integration.sx` — 10 cases: an order-processing flow (validate
+  → payment suspend → branch → ledger federation) and an onboarding flow, run through
+  the full lifecycle including a simulated crash and a peer handoff mid-flow, plus
+  introspection (`flow/pending`/`status`/`result`) during the flow's life
+
 ## Progress log
 
 - **Phase 1 (combinators + sequential runtime).** Flow built as a Scheme prelude