flow: crash recovery — store export/import + resumable scan + 8 tests (Phase 3 complete)

Records are name-keyed (defflow registers names); flow-store-export nulls live
procs to plain data, flow-store-import! restores, flow-resumable-ids scans for
paused flows. Resume re-resolves the proc by name, so a flow survives a wiped
store (simulated restart). The whole durable model persists only plain data.

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

lib/flow/scoreboard.md

@@ -1,6 +1,6 @@
 # flow-on-sx Scoreboard
 
-**All tests pass: 66 / 66 across 3 suites.**
+**All tests pass: 74 / 74 across 4 suites.**
 
 `bash lib/flow/conformance.sh`
 
@@ -11,6 +11,7 @@
 | basic |     18  | Phase 1: single nodes, linear sequence, data-flow threading, defflow, parallel fan/join, nested composition, publish-shaped flow |
 | control |  31  | Phase 2: `branch` (6); error model `fail`/`failed?`/`fail-reason` (6); `try-catch` (6); `retry n` (6); `timeout` cooperative step budget (7) |
 | suspend |  17  | Phase 3: suspend/resume/cancel via deterministic replay; multi-step, replay determinism, lifecycle guards, suspend-in-branch |
+| recovery |  8  | Phase 3: crash recovery — store export/import, resumable scan, restart-at-every-step, replay-log survival |
 
 ## Architecture
 
@@ -38,6 +39,6 @@ capture the flow continuation directly.
 
 - [x] Phase 1 — Declarative DAG + sequential execution (combinators + 18 tests, `flow/start`)
 - [x] Phase 2 — Control flow + error handling (branch, error model, try-catch, retry, timeout)
-- [~] Phase 3 — Suspend/resume (suspend/resume/cancel done via deterministic replay; crash-recovery next)
+- [x] Phase 3 — Suspend/resume (suspend/resume/cancel + crash recovery via deterministic replay)
 - [ ] Phase 3 — Suspend / resume (the showcase)
 - [ ] Phase 4 — Distributed nodes via fed-sx