doe_log.c: add vm_name/vm_id_hex identity columns; new calibration workload

Adds the identity columns HB-ON's existing per-tick CSV logger
(doe_log_tick_row(), doe_log.c) was missing. Previously every column
described *a* VM's state each row, but nothing said which VM emitted
it -- concurrent VMs' rows were indistinguishable by source. Two new
first columns, vm_name and vm_id_hex, resolved via a reverse lookup on
vm->stadium_vm_id (capsule_vm_registry_get()).

Real bug found and fixed while building this: the freestanding
snprintf here silently prints the literal format string instead of
substituting for %016llx (width+ll+hex unsupported) -- caught by
reading the actual emitted row, not assumed to work. Replaced with a
hand-rolled hex nibble-table loop, the same idiom vm_uuid_format()/
MINT-SCRATCH-EMIT already use.

Corrects FABRIC-3.md's own prior "still not started: CSV driver"
framing: no bespoke CSV emitter is needed for the multiuser DoE at
all -- this per-tick logger already exists, fires automatically inside
every VM's own execution loop, and just needed HB-ON plus these
identity columns to be usable for concurrent workers. Also corrects
doe_log.h's own stale doc comment claiming g_doe_log_enabled defaults
to 1 -- doe_log.c's own source is authoritative: 0, off by default,
matching the HB-ON/HB-OFF naming.

One real, honest limitation recorded rather than smoothed over:
vm_name reads blank for any tick captured during a WORKER-BIRTH'd
capsule's own self-execution at birth time, since capsule_birth_baby()
runs that work (and its heartbeat ticks) before the registry name can
be set. vm_id_hex is unaffected (reads directly from vm->stadium_vm_id)
and still uniquely disambiguates every row -- confirmed live: a
blank-name row's own vm_id_hex matched its later PARITY:KILL line's
vm_id exactly.

New workload-calib1.4th: Bob confirmed the existing 10 workload-N.4th
files aren't fixed. Sized to cross HEARTBEAT_CHECK_FREQUENCY (256
word-executions/tick) many times over while staying far lighter than
RUN-FIB/RUN-CHAOS5, both too slow under TCG for a bounded verification
run. A real, reusable addition, not a throwaway.

Verified live on amd64 via a self-contained one-shot EXEC'd test
(HB-ON, WORKER-BIRTH two calibration workers, HB-OFF, VM-ERROR? on
both, KILL both, completion banner) rather than interactive polling,
which breaks once HB-ON makes the log grow continuously via Hera/
Hermes/Artemis's own background ticks. Clean 3-arch qemu boot on the
real committed change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BWpNjdwPtFLuVLaAq44L9K

src/starkernel/doe_log.c

@@ -10,13 +10,29 @@
 /**
  * doe_log.c — DoE CSV logger for the LithosAnanke kernel
  *
- * Emits 20-column CSV rows to the serial log once per heartbeat tick.
- * Each row is prefixed with a cyan [HADES][DOE ] tag so it can be
- * extracted cleanly:
+ * Emits CSV rows to the serial log once per heartbeat tick. Each row is
+ * prefixed with a cyan [HADES][DOE ] tag so it can be extracted cleanly:
  *
  *   grep -aP '\[HADES\]\[DOE \]' qemu-amd64-*.log
  *
  * Columns (in order):
+ *   0a. vm_name                string  — the emitting VM's own registry name
+ *                                        (reverse lookup on vm->stadium_vm_id,
+ *                                        "?" if unregistered at this tick).
+ *                                        Added 2026-09-16 for the multiuser/
+ *                                        multitasking DoE (FABRIC-3.md
+ *                                        §XXXIII): every prior column already
+ *                                        described *a* VM's state each row,
+ *                                        but nothing said *which* VM emitted
+ *                                        it, making concurrent-VM rows
+ *                                        indistinguishable by source.
+ *   0b. vm_id_hex              string  — the emitting VM's own stadium_vm_id
+ *                                        as "hi-lo" hex, same format
+ *                                        PARITY:BIRTH/PARITY:KILL already
+ *                                        print. Names get reused across a
+ *                                        trial's own KILL+rebirth cycles;
+ *                                        this is the one column unique to a
+ *                                        single birth instance.
  *   1.  tick_number           uint32  — monotonic heartbeat counter
  *   2.  elapsed_ns            uint64  — ns since run start
  *   3.  tick_interval_ns      uint64  — actual interval from prior tick
@@ -101,6 +117,7 @@ int g_doe_log_enabled = 0; /* off by default -- HB-ON to enable, per instruction
 
 static const char *doe_header =
     DOE_PREFIX
+    "vm_name,vm_id_hex,"
     "tick_number,elapsed_ns,tick_interval_ns,"
     "cache_hits_delta,bucket_hits_delta,word_executions_delta,"
     "hot_word_count,avg_word_heat_q48,"
@@ -154,6 +171,38 @@ void doe_log_tick_row(VM *vm, const HeartbeatTickSnapshot *snap)
      * for values > 2^32 on aarch64 due to mixed-width varargs ABI behaviour. */
     unsigned vm_call_depth_max = (vm && vm->call_stack_max > 0) ? (unsigned)vm->call_stack_max : 0;
 
+    /* Identity columns (2026-09-16, FABRIC-3.md §XXXIII): reverse-lookup
+     * this row's own emitting VM by its stadium_vm_id -- name can be
+     * reused across a KILL+rebirth cycle, so vm_id_hex is what actually
+     * disambiguates one birth instance from the next. "?" name / all-zero
+     * id if vm is NULL or not (yet) registered, never a crash. */
+    const char *vm_name = "?";
+    char        vm_id_hex[34] = "0000000000000000-0000000000000000";
+    if (vm) {
+        VMRegistryEntry self_entry;
+        if (capsule_vm_registry_get(vm->stadium_vm_id, &self_entry) == 0) {
+            vm_name = self_entry.name;
+        }
+        /* Hand-rolled hex, not snprintf("%016llx", ...) -- found live
+         * (2026-09-16) that this freestanding snprintf doesn't support
+         * width+ll+x and silently prints the literal format string
+         * instead of substituting. Same nibble-table idiom vm_uuid.c's
+         * own vm_uuid_format() and MINT-SCRATCH-EMIT already use. */
+        {
+            static const char hexd[] = "0123456789abcdef";
+            uint64_t halves[2] = { vm->stadium_vm_id.hi, vm->stadium_vm_id.lo };
+            int pos = 0, h;
+            for (h = 0; h < 2; h++) {
+                int i;
+                for (i = 15; i >= 0; i--) {
+                    vm_id_hex[pos++] = hexd[(halves[h] >> (i * 4)) & 0xF];
+                }
+                if (h == 0) vm_id_hex[pos++] = '-';
+            }
+            vm_id_hex[pos] = '\0';
+        }
+    }
+
     uint64_t hera_heat_q48    = doe_log_heat_by_name("Hera");
     uint64_t hermes_heat_q48  = doe_log_heat_by_name("Hermes");
     uint64_t artemis_heat_q48 = doe_log_heat_by_name("Artemis");
@@ -180,8 +229,11 @@ void doe_log_tick_row(VM *vm, const HeartbeatTickSnapshot *snap)
 
     char buf[DOE_BUF_SIZE];
     snprintf(buf, sizeof(buf),
+             "%s,%s,"
              "%u,%llu,%llu,%u,%u,%u,%llu,%llu,%u,%u,%u,%llu,%llu,%llu,%llu,%u,%llu,%llu,%llu,%llu,%u,"
              "%llu,%u,%u,%u,%u,%u",
+             vm_name,
+             vm_id_hex,
              snap->tick_number,
              (unsigned long long)snap->elapsed_ns,
              (unsigned long long)snap->tick_interval_ns,