Enforce heartbeat_timeout_ms >= 2 * heartbeat_interval_ms at startup.
validate_heartbeat_config() in startup_validation.c returns -EINVAL with
error message on violation; wired in cluster_init_phase1 before ha_init().
4 unit tests added to test_ha_startup.c.
Add time_t last_activity to ha_state_t for standby liveness timestamp tracking.
Add time_t last_push_time to standby_ep_ctx_t for primary idle NOP suppression.
Zero-initialize last_activity in ha_init(); last_push_time zeroed by calloc.
Add test_ha_init_last_activity_is_zero to test_ha_startup.c.
- sem_timedwait on heartbeat_seen semaphore with CLOCK_REALTIME deadline
- deadline = now + election_timeout_ms + xorshift64 jitter
- Returns CTRL_STANDBY on heartbeat arrival (calls ha_do_demote)
- Returns CTRL_ELECTING on timeout (caller drives election)
- Allows OPCode_heartbeat through dispatch gate in CTRL_INIT state
- 3 new unit tests: standby-on-heartbeat, electing-on-timeout, gate-allows-heartbeat
- 24 Tests 0 Failures in test_ha_startup suite
RED-phase tests for 4 startup validation functions — all fail at link time
because the functions under test do not exist yet:
- validate_peer_count: even N>1 returns -EINVAL, odd N returns 0
- validate_cert_files: missing cert/key returns -ENOENT with full path
in err_buf output param (asserted via strstr)
- validate_vcpus: vcpus<=0 returns -EINVAL, positive returns 0
- validate_startup_config: vcpus key in config returns 0 (not fatal)
and writes deprecation text into warn_buf (asserted via strstr)
