feat(ha-repl-hardening): committing timeout 60s degraded-mode safety net (task 5.3)

- Change HA_DEFAULT_COMMITTING_TIMEOUT_MS from 10000 to 60000
- committing_timeout_fn: count converged/pending standbys from
  standby_converged[], log WARN with counts, then promote (degraded mode)
- Replace hardcoded 10000 in test_ha_evaluate_committing.c with macro
- Three new tests: default=60000, degrade-promote with 1/2 and 0/2 converged

src/controller/testsuite/test_ha_evaluate_committing.c

@@ -60,7 +60,7 @@ static ha_config_t g_cfg = {
     .max_promotion_retries     = 5,
     .election_jitter_max_ms    = 0,
     .election_priority_step_ms = 500,
-    .committing_timeout_ms     = 10000,
+    .committing_timeout_ms     = HA_DEFAULT_COMMITTING_TIMEOUT_MS,
 };
 
 /* ── Helper: build a minimal ha_elect_ctx_t for n_other peers ───────────── */