* fix: keep fleet prune estimate bytes after a target timeout
Accumulate successful per-target reclaimable bytes on both the local
serial loop and the remote fan-out, mark partial nodes, and surface that
state in the Fleet prune card instead of zeroing the whole node.
* test: clarify zero-byte partial estimate card case
Rename the FleetPruneCard assertion so it matches fold semantics:
partial with zero bytes means a successful zero-byte target plus a failure,
not an all-failed node.
* fix: keep fleet prune estimate resilient on init and partial errors
Guard DockerController init so a deleted-node race cannot 500 the whole
fleet estimate, surface partial-node failure text in the card row title,
and pin the generic-rejection partial path with a fast route test.
* test: destroy reverse-route connect-ack sockets on teardown
Unguarded accepted sockets could emit a late ECONNRESET after assertions passed, failing the Backend Vitest job with zero assertion failures.
Anso