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>

lib/flow/conformance.sh

@@ -29,6 +29,7 @@ SUITES=(
   "api         flow-api-tests-run!       lib/flow/tests/api.sx"
   "combinators flow-cmb-tests-run!       lib/flow/tests/combinators.sx"
   "railway     flow-rail-tests-run!      lib/flow/tests/railway.sx"
+  "integration flow-int-tests-run!       lib/flow/tests/integration.sx"
 )
 
 TMPFILE=$(mktemp); trap "rm -f $TMPFILE" EXIT