flow: operational introspection API — flow/status,result,list,pending + 12 tests

flow/status id -> done|suspended|cancelled|unknown; flow/result id -> value or
error; flow/list -> (id status) per flow; flow/pending -> (id waiting-tag) for
suspended flows (operator view of what each awaits). Pure store introspection.

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: 93 / 93 across 5 suites. All four phases complete.**
+**All tests pass: 105 / 105 across 6 suites. Phases 1-4 complete; Phase 5 in progress.**
 
 `bash lib/flow/conformance.sh`
 
@@ -13,6 +13,7 @@
 | 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 |
 | distributed | 19 | Phase 4: `remote-node` (7); `remote-failover` (6); replication + handoff across instances (6) |
+| api |  12  | Phase 5: introspection — `flow/status`, `flow/result`, `flow/list`, `flow/pending` |
 
 ## Architecture
 
@@ -42,5 +43,6 @@ capture the flow continuation directly.
 - [x] Phase 2 — Control flow + error handling (branch, error model, try-catch, retry, timeout)
 - [x] Phase 3 — Suspend/resume (suspend/resume/cancel + crash recovery via deterministic replay)
 - [x] Phase 4 — Distributed nodes via fed-sx (remote-node, failover, replication + handoff)
+- [~] Phase 5 — Operational API + combinators (introspection done; tap/recover/map-flow next)
 - [ ] Phase 3 — Suspend / resume (the showcase)
 - [ ] Phase 4 — Distributed nodes via fed-sx