raft_sim_restart_node models a process restart: the durable in-memory log[]
(WAL) and persisted (term, voted_for) survive, while volatile consensus state
is cleared by re-running raft_init (returns the node to FOLLOWER). Callbacks,
ctx, idx, and partition flag are preserved.
test_sim_9_5_node_restart_resumes_replication restarts a follower mid-replication
(partial 2-of-3 log), asserts the log survived (load-bearing: log_count==2 would
fail if wiped), role/term restored, then replication resumes and converges with
Log Matching. Closes the 8.3 'node restart while replication proceeds' sub-clause
(8/8 requirement sections now fully covered). ASAN green (220 tests).