fix(harness): xce_test argument validation, RPC error text and leaks (13 bugs)

Stack overflows on user input:
- bug-1702 jobrun -m: host segment strncpy'd into a 256-byte buffer
  unbounded (ASAN stack-buffer-overflow); now cmdutil_split_host_tasks()
  refuses an over-long host.
- bug-1703 jobsub -n: min strncpy'd into a 64-byte buffer; now
  cmdutil_parse_ntasks() parses in place, 1 <= min <= max.
- resupdate's 16-entry vals[] had no bound either; a 17th -n overflowed.

Wrong or silent results:
- bug-1574 resupdate type/model: set_resval() had no string case, left the
  entry's name uninitialized, and crashed the encoder. Moved to
  resval_typeresolve.c as resval_fill(), which fills every type.
- bug-1705 jobsub -x was overwritten (and leaked) by the default exdata;
  cmdutil_default_exdata() only fills an unset one. jobsub's
  execuser/exechome/execcwd copies leaked on every call.
- bug-1707 a trailing -n without -v was dropped silently; resupdate also
  returned 0 after its RPC failed and "succeeded" with nothing to send.
- bug-1708 jobkill -s SIGKILL became signal 0 and was sent.
- bug-1709 jobinfo exited 0 with no -j, a malformed -j, or no hits.
- bug-1710 hello -c 0 sent nothing and reported success.
- bug-1712 a duplicate -v was reported as "no res name found".
- bug-1777 workerlist showed join-time maxmem/maxswap/maxtmp, not the
  effective values (hosts.yaml overrides) the reply already carries in
  resvals_to_sched and the scheduler uses.
- bug-1793 join's maxswap/maxtmp defaults were 1 KB / 2 KB in bytes; now
  1 GiB / 2 GiB, and -m/-s/-t no longer overflow atoi() above 2 GB.

Error reporting and leaks:
- bug-1796 RPC failures printed perror() of a stale errno ("Connection
  refused" / "Invalid argument" / "Inappropriate ioctl for device" for
  the same failure). cmdutil_rpc_error() prints the RPC's own code
  (E_XCE_* included) at all 19 sites.
- bug-1797 qctrl leaked the queue name on the RPC-error path; repeated
  -q/-h leaked the earlier copy.

New src/harness/cmdutil.c (+ cmdutil_unit_test, 14 cases); 9 new
test_test_cli.c cases, 8 RED on the old xce_test; new resval_fill,
worker_effective_attr and join-default tests (join ones RED on the old
join_worker_args.c). Harness suite 6/6 (asan), harness_unit_test 141/0.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/harness/joblist_display.c

@@ -7,6 +7,7 @@
 #include "joblist_display.h"
 
 #include <stdio.h> /* snprintf */
+#include <string.h> /* strcmp */
 
 #include "xce/ctrlstatus_fmt.h" /* ctrlstatus_format_time_ms */
 #include "xce/types.h"      /* XCE_WORKER_*, JOB_STAT_* bit definitions */
@@ -97,3 +98,34 @@ const char* format_job_time(time_t t, char* buf, size_t bufsize)
 
     return buf;
 }
+
+double worker_effective_attr(const xce_worker_t* w, const char* resname,
+                             double attr_value)
+{
+    if (w == NULL) {
+        return attr_value;
+    }
+    for (int i = 0; i < w->nresvals_to_sched; i++) {
+        const xce_name_val_t* nv = w->resvals_to_sched[i];
+
+        if ((nv == NULL) || (nv->name == NULL) || (nv->val == NULL)
+            || (strcmp(nv->name, resname) != 0)) {
+            continue;
+        }
+        switch (nv->val->which) {
+        case Value_u_fvalue:
+            return nv->val->u.fvalue;
+        case Value_u_ivalue32:
+            return (double)nv->val->u.ivalue32;
+        case Value_u_uvalue32:
+            return (double)nv->val->u.uvalue32;
+        case Value_u_ivalue64:
+            return (double)nv->val->u.ivalue64;
+        case Value_u_uvalue64:
+            return (double)nv->val->u.uvalue64;
+        default:
+            return attr_value; /* not numeric */
+        }
+    }
+    return attr_value;
+}