refactor(controller,xceadmin): drop generic Resource.unit, hardcode bytes for maxmem

Simplification per review feedback on e3b3ffa: a generic schema-driven
unit field touched the capnp wire schema (2 structs), C structs
(xce_resource_t/xce_resval_t), resobj.c's deep-copy/destroy, opget.c's
reply-build lookup, resources.yaml/resources.schema.json, and mapping.py
-- real cross-cutting cost for a mechanism only one resource (maxmem)
actually needs today.

Reverted all of that. The controller CLI (test.c) now just knows
"maxmem" is bytes-valued via a small explicit is_bytes_valued_resource()
name list, and adaptively picks the best-fit human unit at display time
(format_bytes_human, unchanged) -- same observable behavior (resval/
workerlist render maxmem as e.g. "30.90 GB"), zero wire schema surface.
Regenerated the xceadmin golden fixture back to its pre-unit-field size
(5304 bytes, exactly matching the size right after the mxj-only fix,
confirming a clean, complete removal).

Verified: 1095/1095 controller_unit_test (3 runs; one hit the
pre-existing flaky segfault already logged as bug-1553, unrelated),
228/228 xceadmin pytest, clean rebuild of lib/controller/xceadmin/xce_test.

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

src/controller/opget.c

@@ -62,20 +62,9 @@ static int do_reply_resvals(cluster_t* c, endpoint_t* ep,
             rc            = get_resval(c, condition->condition.reskey->resname,
                                        condition->condition.reskey->hostname, &val);
             if (rc >= 0) {
-                xce_resource_t* r = NULL;
-
                 resval.val         = &val;
                 resval.name        = condition->condition.reskey->resname;
                 resval.host        = condition->condition.reskey->hostname;
-                resval.unit        = NULL;
-
-                lock(c->resmgr, RTTI_LOCK_READ);
-                key_find(c->resmgr, (void*)resval.name, (void**)&r);
-                unlock(c->resmgr);
-                if (r != NULL) {
-                    resval.unit = r->unit;
-                }
-
                 resvaldata.n_total = 1;
                 resvaldata.vals    = vals;
             }

src/controller/testsuite/test.c

@@ -2036,11 +2036,40 @@ cleanup:
 }
 
 /*
- * Render a raw byte count as a human-readable string (e.g. "30.90 GB").
- * Only used for display -- the stored/wire value stays raw bytes always,
- * this never feeds back into anything that's compared or persisted. A
- * pure function so it's directly unit-testable without a live client
- * connection.
+ * Resource names whose canonical stored/wire value is raw bytes (not a
+ * generic schema-driven unit system -- deliberately kept as a small,
+ * explicit, client-side list rather than a wire field, since exactly one
+ * resource needs this today and a wire-level unit hint would have grown
+ * every Resource/ResourceVal message regardless of whether it's used).
+ * CLI display picks the best-fit human unit adaptively (format_bytes_human);
+ * the stored value is never converted.
+ */
+static int is_bytes_valued_resource(const char* name)
+{
+    static const char* const BYTES_VALUED_RESOURCES[] = { "maxmem" };
+    const int nres = (int)(sizeof(BYTES_VALUED_RESOURCES)
+                           / sizeof(BYTES_VALUED_RESOURCES[0]));
+    int       i;
+
+    if (name == NULL) {
+        return 0;
+    }
+
+    for (i = 0; i < nres; i++) {
+        if (strcmp(name, BYTES_VALUED_RESOURCES[i]) == 0) {
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+/*
+ * Render a raw byte count as a human-readable string (e.g. "30.90 GB"),
+ * adaptively picking the smallest unit the value fits in. Only used for
+ * display -- the stored/wire value stays raw bytes always, this never
+ * feeds back into anything that's compared or persisted. A pure function
+ * so it's directly unit-testable without a live client connection.
  */
 static void format_bytes_human(double bytes, char* buf, size_t bufsize)
 {
@@ -2098,7 +2127,7 @@ int cmd_resval(int argc, char* argv[])
                 printf("%s\n", val->val->u.svalue);
                 break;
             case Value_u_fvalue:
-                if ((val->unit != NULL) && (strcmp(val->unit, "bytes") == 0)) {
+                if (is_bytes_valued_resource(val->name)) {
                     char hbuf[64];
 
                     format_bytes_human(val->val->u.fvalue, hbuf,