conduit explain does not show the child flow of a kind: subflow station

[queso]

Problem

conduit explain renders a kind: subflow station like any other station. It does not show which child flow the station calls.

renderFlow (src/cli/explain-renderer.ts:359) prints each station with its kind glyph (src/cli/explain-renderer.ts:161) and never reads worker.flow. The composition data already exists:

• Statically, the station's flow path (src/controller/executor.ts:4214).
• At run time, every subflow attempt writes a <station>.subflow journal span that carries child_run_id (src/controller/executor.ts:4309-4344).

Ask

• Flow view: render a kind: subflow station with the child flow it calls (name and path), so that explain of a composing flow shows the composition.
• Run view (if explain gains a run mode): render the parent run to child run edge from the journaled child_run_id, so an operator can follow a run into its child.

This is a renderer change only; no new instrumentation is needed. Keep it consistent with how fan-out child lanes are rendered.

Acceptance criteria

• conduit explain on a flow with a kind: subflow station prints the child flow's path next to the station.
• The existing explain renderer tests still pass.