fix(controller,xceadmin): fix zero-slot scheduling block, misleading resval logs, byte-unit display

Three bugs found while diagnosing a live controller log, all in the
worker resource-value path:

1. Every host relying on the documented hosts.yaml auto-detect default
   (no max_slot, meaning "use CPU count") got 0 scheduling slots,
   permanently blocking the scheduler from placing jobs on it. mxj is
   UInt32 on the wire and can't carry the schema's -1 sentinel; mapping.py
   worked around this by leaving it unset, which defaults to 0 -- and 0 is
   never < 0, so apply_join_state()'s auto-detect fallback never fired.
   Fixed by encoding the sentinel as 0xFFFFFFFF, which the controller's
   `int mxj` field reinterprets back to -1 via its existing implicit
   uint32_t->int conversion. No C-side or wire schema change needed for
   this part; the fallback itself was already correct but had zero test
   coverage for a negative mxj, now added.

2. update_resvals()/update_resval_list() logged the failure reason via
   PERROR, which reads process-global errno -- but update_resval()'s
   failure paths return raw negative codes directly and never touch
   errno, so the controller log filled with misleading "update_resval:
   Success" / "update_resval: Resource temporarily unavailable" lines
   instead of the real reason. Fixed to decode the actual rc via
   xce_strerror_r and name the failing resource.

3. maxmem is canonically stored/wired as raw bytes but had no unit
   metadata, so resval/workerlist printed it as a bare number that read
   as garbage (e.g. workerlist's fixed-width columns visually smeared a
   multi-GB byte count across the MaxCPU/MaxMem headers). Added an
   optional `unit` field to the Resource/ResourceVal capnp structs (and
   xce_resource_t/xce_resval_t/resources.yaml) so resval and workerlist
   can render a human-readable value (e.g. "30.90 GB") while the stored
   value stays raw bytes -- display-only, every other resource unaffected.

Regenerated the xceadmin golden fixture (fixtures/full/expected.bin)
twice: once for the mxj sentinel encoding change, once for the new
Resource.unit field growing every resource's wire size by one pointer
slot. Both diffs verified byte-for-byte isolated to exactly the expected
change before regenerating.

Verified: 1095/1095 controller_unit_test (stable across repeated runs),
229/229 xceadmin pytest, clean rebuild of lib/controller/xceadmin/xce_test.
Two related findings logged to .wolf/buglog.json but deliberately not
fixed here (out of scope per discussion): a pre-existing flaky segfault
in the combined controller_unit_test binary, and maxswap/maxtmp being
hardcoded stub values on the worker side.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/controller/worker.c

@@ -115,7 +115,7 @@ static int update_resval(cluster_t* c, worker_t* w, xce_resval_t* val)
     }
     if (r == NULL) {
         ERROR("resource `%s' can not be found", val->name);
-        return -errno;
+        return -ENOENT;
     }
 
     if (r->idx < 0) {
@@ -130,6 +130,24 @@ static int update_resval(cluster_t* c, worker_t* w, xce_resval_t* val)
     return rc;
 }
 
+/*
+ * update_resval() returns its failure reason as a raw negative code
+ * directly (key_find/zarray_put convention throughout this codebase --
+ * never via errno), so logging it with PERROR (which reads the process-
+ * global errno) reported whatever errno happened to be left over from an
+ * unrelated earlier call -- "Success" if nothing had touched it, or a
+ * stray EAGAIN/etc from some other syscall in the same event-loop
+ * iteration, never the real reason. Decode the actual rc instead.
+ */
+static void log_update_resval_failure(const char* name, int rc)
+{
+    char ebuf[128];
+
+    ebuf[0] = '\0';
+    xce_strerror_r(-rc, ebuf, sizeof(ebuf));
+    ERROR("update_resval `%s': %s", name, ebuf);
+}
+
 int update_resvals(cluster_t* c, worker_t* w, int nres, xce_resval_t* vals)
 {
     int rc = 0;
@@ -138,7 +156,7 @@ int update_resvals(cluster_t* c, worker_t* w, int nres, xce_resval_t* vals)
     for (i = 0; i < nres; i++) {
         rc = update_resval(c, w, &(vals[i]));
         if (rc < 0) {
-            PERROR("update_resval");
+            log_update_resval_failure(vals[i].name, rc);
         }
     }
 
@@ -153,7 +171,7 @@ int update_resval_list(cluster_t* c, worker_t* w, xce_resval_list_t* l)
     for (i = 0; i < l->count; i++) {
         rc = update_resval(c, w, l->vals[i]);
         if (rc < 0) {
-            PERROR("update_resval");
+            log_update_resval_failure(l->vals[i]->name, rc);
         }
     }