fix(election-iomgr-refactor): correct task 2.4 review findings

- CRITICAL: single-node shortcircuit enters CTRL_PRIMARY_COMMITTING
  (not CTRL_PRIMARY directly); phase2 transition deferred to task 4.x
- CRITICAL: add n_peers==0 guard in ha_elect_evaluate_and_signal to
  prevent votes[0] out-of-bounds access
- HIGH: wire client_ssl_ctx after endpoint_connect for outgoing votes
- HIGH: add timeout_ctx field to ha_elect_ctx_t for task 4.x cancel
- HIGH: clarify vote_ep_err_handler ownership (no premature free of vctx;
  deferred to ha_election_cleanup in task 5.1)
- Tests updated: single-node shortcircuit asserts COMMITTING not PRIMARY

src/controller/ha.h

@@ -92,6 +92,10 @@ typedef struct {
     int              done_posted;      /* Guard: non-zero once sem_post(&done) has been called */
     pthread_mutex_t  lock;             /* Protects votes_granted/n_replied/max_resp_tag/max_resp_lsn/result */
     sem_t            done;             /* Startup thread blocks; dispatch posts when done */
+    /* Fix 4 (HIGH): pointer back to the election_timeout_ctx_t so that task 4.1
+     * (quorum-reached path) can set timeout_ctx->cancelled = 1 to cancel the
+     * watchdog.  Set by ha_start_election_async after scheduling the timeout. */
+    void            *timeout_ctx;      /* election_timeout_ctx_t*; NULL until watchdog scheduled */
     ha_vote_entry_t  votes[];          /* C99 flexible array: n_peers-1 entries */
 } ha_elect_ctx_t;