Phase C: distributed messaging capsule + idle-loop pump

Extract the messaging vocabulary (arenas, MSG-*/CH-*/MBR-* words) out of
capsules/hermes/init.4th into a new shared capsules/common/messaging.4th
that Hermes and Artemis each load at birth, giving every VM its own
private MSG-ARENA/CH-ARENA instead of only Hermes having one. Hermes
stays the owner of the one real, canonical COMMON-CH; Artemis subscribes
into it via VM-EXEC at her own birth, and Hermes proactively subscribes
Hera (idx 0) since Hera always exists first.

Hera does NOT get her own copy: register_child_vm_words()'s own doc
comment explains why the STADIUM-* primitives common:messaging.4th
depends on are deliberately never registered in her dictionary (keeps
her dict_hash off item 4.1's baseline). Confirmed live by loading it
into her dictionary anyway first -- every colon-definition referencing
an unregistered Stadium primitive was silently dropped (MSG-HEAT@/!,
CH-HEAT@/!, MSG-COOL-ALL, MSG-TICK all missing after boot). Reverted
that path; she orchestrates via BIRTH/VM-EXEC/VM-CALL instead.

Added capsule_vm_registry_get_by_index() (capsule_birth.c/.h) for
registry enumeration by birth-order position, and a pump in repl.c's
existing idle hook that walks every live VM once per idle beat and
VM-EXECs MSG-TICK into each one except Hera's own entry.

Verified clean (no UNKNOWN WORD / VM-EXEC errors after birth) on all
three architectures.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019ZGkimpfyh63EZyRkNbkPD

src/starkernel/capsule/capsule_birth.c

@@ -199,6 +199,18 @@ uint32_t capsule_vm_registry_count(void) {
     return vm_registry_count;
 }
 
+int capsule_vm_registry_get_by_index(uint32_t index, VMRegistryEntry *out) {
+    vm_node_t *node = vm_registry_head;
+    uint32_t   i    = 0;
+    if (!out) return -1;
+    while (node) {
+        if (i == index) { *out = node->entry; return 0; }
+        node = node->next;
+        i++;
+    }
+    return -1;
+}
+
 /* Live population, distinct from vm_registry_count above: vm_registry_count
  * is monotonic (incremented on every vm_registry_alloc(), never decremented
  * on death), so it counts every VM ever born, not the outer Stadium's

src/starkernel/kernel_main.c

@@ -813,6 +813,20 @@ static void kernel_main_deep(BootInfo *boot_info) {
         }
     }
 
+    /* Phase C (2026-08-28): Hera does NOT get her own common:messaging.4th
+     * arena -- register_child_vm_words()'s own doc comment (mama_forth_
+     * words.c) explains why: the eight STADIUM-* FORTH primitives that
+     * word depends on (CH-HEAT@/!, MSG-HEAT@/! etc. all route through
+     * them) are deliberately never added to register_mama_forth_words(),
+     * to avoid moving Hera's dict_hash off item 4.1's baseline. Confirmed
+     * live: loading messaging.4th into Hera's own dictionary silently
+     * dropped every colon-definition that referenced one of those
+     * primitives (MSG-HEAT@/!, CH-HEAT@/!, MSG-COOL-ALL, MSG-TICK all
+     * missing after boot) -- not a timing bug, a real, pre-existing
+     * constraint. Hera orchestrates via BIRTH/VM-EXEC/VM-CALL directly
+     * instead; the idle-loop pump (repl.c) skips her own registry entry
+     * for the same reason. */
+
     /* Hermes is now a permanent fleet-foundation VM, not self-test
      * scaffolding -- FABRIC-3.md D.7 (birth-by-message-only, 2026-08-28):
      * the Tripod legs (Hera/Hermes/Artemis) must be alive session-less so

src/starkernel/repl.c

@@ -37,6 +37,9 @@
 #include "starkernel/xhci_driver.h"
 #include "starkernel/blkio_usb.h"
 #include "starkernel/homeblocks_sig.h"
+#include "starkernel/capsule_birth.h"
+#include "starkernel/capsule_run.h"
+#include "starkernel/vm/bootstrap/sk_vm_bootstrap.h"
 #include "block_subsystem.h"
 #include "word_source/include/keyboard_words.h"
 #include "word_source/include/block_words.h"
@@ -185,6 +188,44 @@ static void sk_repl_idle(VM *active_vm)
      * write with no UPDATE, followed by an idle wait and an abrupt kill,
      * did not survive a reboot until this fix. */
     blk_vm_flush_all(active_vm);
+
+    /* FABRIC-3.md Phase C (2026-08-28): distributed messaging pump. Every
+     * live VM except Hera herself now owns its own MSG-ARENA/CH-ARENA and
+     * MSG-TICK word (see capsules/common/messaging.4th) instead of only
+     * Hermes having one -- "fully distributed, Hera pumps each VM's
+     * drain" was the confirmed design. Hera is excluded: she never loads
+     * common:messaging.4th (kernel_main.c's own comment at the Hermes-
+     * birth call site explains why -- the STADIUM-* primitives it needs
+     * are deliberately never registered in her own dictionary, to keep
+     * her dict_hash off item 4.1's baseline), so MSG-TICK is genuinely
+     * absent there, not just untried. She is the only VM with a
+     * persistent idle tick, so she walks the registry once per idle beat
+     * and VM-EXECs MSG-TICK into every OTHER live VM's own dictionary. */
+    {
+        VM      *mama  = (VM *)sk_get_mama_vm();
+        uint32_t count  = capsule_vm_registry_count();
+        uint32_t i;
+        for (i = 0; i < count; i++) {
+            VMRegistryEntry ent;
+            if (capsule_vm_registry_get_by_index(i, &ent) != 0) continue;
+            if (ent.state != VM_STATE_LIVE) continue;
+            if (ent.vm_ptr == (void *)mama) continue;
+
+            static const char PFX[] = "S\" MSG-TICK\" S\" ";
+            static const char SFX[] = "\" VM-EXEC";
+            char   cmd[128];
+            size_t p = 0;
+            size_t name_len = strlen(ent.name);
+            if (name_len > VM_NAME_MAX - 1u) name_len = VM_NAME_MAX - 1u;
+
+            memcpy(cmd + p, PFX, sizeof(PFX) - 1u); p += sizeof(PFX) - 1u;
+            memcpy(cmd + p, ent.name, name_len);    p += name_len;
+            memcpy(cmd + p, SFX, sizeof(SFX) - 1u); p += sizeof(SFX) - 1u;
+            cmd[p] = '\0';
+
+            vm_interpret(mama, cmd);
+        }
+    }
 }
 
 /*===========================================================================