I've extracted the network cleanup step from `delete` into a new public
`releaseNetwork` method. This mirrors the existing `release` on
`VmnetNetwork` and enables stop-and-restart workflows where the network
allocation needs to be freed without removing the container's rootfs.
## Changes
- Add `ContainerManager.release(_:)` — frees network resources for a
container after it has stopped
- Refactor `delete(_:)` to call `releaseNetwork(_:)` before removing
files, preserving existing behavior
## Motivation
Currently the only way to free a container's network allocation is
`delete`, which also removes its files. This makes it impossible to stop
a container (freeing the network so the ID can be re-allocated) and
later restart it with its filesystem intact. The new `releaseNetwork `
method fills this gap.
Anthony
9bce347f50