feat(config-upgrade-snapshot): live config-upgrade soak infra + fix bug-1468/bug-1469 (task 8.6)

Build the live 3-node chaotic-multi-kill config-upgrade soak scenario
(run-ha-soak.sh --config-upgrade) required by Requirements 4.1, 4.3, 6.1,
6.4. This needed genuinely new client-side infrastructure: a hand-rolled
capnp send path for OP_upgradeConfig (the auto-generated encoder is a
no-op for its Data fields, worked around the same way
xce_replconfigpush_req_raw already does), plus cmd_hostctrl/cmd_upgradeconfig
CLI commands.

Building and running this live surfaced two real production bugs, both
fixed here:

- bug-1468: an unrelated prior commit inverted OPCode_upgradeConfig's
  primary/standby dispatch guard in cluster.c, making config upgrades
  unreachable from any network client.
- bug-1469: apply_committed_entry's WAL_CONFIG_MARKER case never called
  config_activate_committed(), so the node that originates a config
  upgrade never refreshed its own in-memory state as part of committing
  it. Killing that node before some later, unrelated event happened to
  refresh it left its checkpoint permanently stale -- the first live,
  empirical reproduction of bug-857's originally hypothesized failure
  mode. Fixed by activating before the marker-triggered checkpoint write,
  since checkpoint content is built from live runtime tables that only
  reflect the reload after activation runs.

A separate, narrower checkpoint divergence (bug-1471, not config-related)
remains open and still blocks a clean soak PASS -- task 8.6 stays
in-progress until it's resolved.

src/include/request.h

@@ -185,6 +185,19 @@ extern int xce_upgrade_config_req_extract_raw(const uint8_t *pkt_data,
                                                size_t   *out_len,
                                                uint8_t **out_sha256);
 
+/*
+ * xce_upgradeconfig_req_raw: send OP_upgradeConfig carrying raw byte arrays
+ * (sha256 + the serialised ClusterConfig blob). Bypasses the generated
+ * encode_UpgradeConfigRequest path (a no-op for the sha256/bytes Data fields
+ * — same class of limitation as xce_replconfigpush_req_raw) by constructing
+ * the capnp message directly via capn_new_list8 + capn_setv8 + write_Request.
+ * Ordinary CLIENT request: seq/from are populated the same way xce_request()
+ * populates them for every other client op.
+ */
+extern int xce_upgradeconfig_req_raw(endpoint_t *ep,
+                                     const uint8_t *sha256, size_t sha256_len,
+                                     const uint8_t *bytes, size_t bytes_len);
+
 /* ── Client-Side Transparent Retry tunables (Req 6.1, 6.2) ──────────────────
  *
  * xce_retry_config_t: configurable retry parameters with safe production