Task 7.1 (unit tests) was already complete with 8 tests in
test_ha_connection_reuse.c. Added two new tests:
Task 7.2 — test_follower_passive_no_outbound_connect (Req 2.1, 2.4):
Verifies raft_cb_become_follower sets role=CTRL_STANDBY and nulls all
votes[i].ep. The old fetch_config_from_primary path is gone; standbys
never initiate outbound connects after election loss.
Task 7.3 — test_promoted_ep_repl_ack_promotes_to_primary (Req 5.2, 5.4):
Injects two OPCode_replCatchUpDone packets via peer_ctrl_msg_handler in
CTRL_PRIMARY_COMMITTING with n_peers=4 (5-node cluster, quorum=2 ACKs).
Verifies repl_ack_count reaches 2 and role transitions to CTRL_PRIMARY.
Added vote_ep_ctx_set_cluster_for_test() seam so vctx->c is non-NULL
when ha_repl_ack_received fires ha_promote_to_primary.
All 62 controller tests pass; ASAN clean.
spec: .kiro/specs/ha-peer-connection-reuse/tasks.md all tasks [x]
