flowtest: virtual elapsed time is printed and cannot be asserted, and a `for_each` with `max_parallel:` is not a scheduling junction for `--seeds`

Observed behavior

Time is visible and unassertable. The virtual clock is the format's best feature: a run sleeping a day resolves in milliseconds and the transcript prints t=24h0m5s beside each event. The check: root exposes run as {failed, error, local} only (pkg/flowstate/v1/flowtest/check.go:233-244), so a case cannot claim "this run took under two hours of virtual time" or "the gate lapsed at exactly 24h". An SLA-shaped workflow (the twelfth round of DSL.md, three clocks) has no test that reads a clock.

Fan-out is not explored. flow test --seeds 5 examples/matrix-fan-out/ and examples/paged-fan-out/ report 0 scheduling decisions although both use for_each with max_parallel: 3. --seeds explores parallel: and async: junctions only (clock.go:25-32), so the fan-out examples, the construct most likely to hide an order dependence in a real workload, get no exploration and the report does not say why.

Desired outcome

• check: gains run.elapsed (a duration) and run.ended_at (a timestamp on the virtual clock), plus per-step steps.<id>.started_at/ended_at where the transcript already has them, so check: run.elapsed < duration('2h') is a claim.
• --seeds treats a for_each with max_parallel > 1 as a junction over iteration completion order, or the summary line states that fan-out order is not explored and why.

Acceptance criteria

• examples/approval-escalation gains one case asserting the lapse time through run.elapsed.
• flow test --seeds 5 examples/matrix-fan-out/ reports at least one decision, or its report names the construct it did not explore.
• Both drivers agree on the virtual timestamps a case can read: the durable driver's timeline for the same file shows the same relative times, pinned by a conformance case.

Constraints and dependencies

• Adjacent: #1598 (--driver durable), #477 (deterministic simulation tier), #1594 (--fuzz).

Start with pkg/flowstate/v1/flowtest/check.go:233-244 for the check root and clock.go:25-32 for the --seeds junctions. Inspect the approval-escalation, matrix-fan-out, and paged-fan-out examples, then compare both drivers using the referenced durable-driver and conformance work. Done means elapsed and timestamp assertions work, fan-out is explored or explained in the report, and both drivers agree on virtual times.