feat(kernel): v4 boots in the kernel's boot -- the Stadium, its checks, the opcode patrons

#189, ENGINE step 4, Phase 1 (plan 2026-11-13-engine-step4-phase1), Tasks
1-4. Captain Bob, 2026-11-13: Q1 "A new node key", Q2 "Per heartbeat
tick", Q3 "All of v3's", Q4 "In Phase 1" / "Full births now", who runs
next "Hera by compudynamics now" (Task 5, to come).

- stadium.c/.h: stadium_node_key(node) ("NODE" | number),
  stadium_boot_init_for(first), stadium_birth_node(key, name);
  stadium_boot_init() and stadium_birth_hera() are them for Hera's key, so
  v3's path is as it was (only an impossible panic's words changed).
- kernel_main.c: the system is chosen and said first, then the Stadium,
  sessions, switch-signal and kernel-Hermes tables for both systems in
  v3's order; v4: Hera, node 10, patron zero under her node key, the word,
  block and opcode layers. The quota self-test and the heartbeat's line
  are functions now, called by both systems.
- sk_v4.c/.h: sk_v4_run() goes -- sk_v4_boot() returns, the kernel's
  checks after POST (opcodes, words, conservation, quota, heartbeat), then
  sk_v4_prompt(). sk_v4_charge_opcodes() at the heartbeat's service points
  (the key wait, after each line) and once after POST.
- stadium_ops.c/.h: a node's 32 opcodes as Stadium patrons (HEAT-OP's
  feed, "Both"): retirements charged as the word layer's dispatches, a
  quantum each, the reservoir's floor kept, shared by retirements when
  short; cooling per tick as words. ~0.5 us a charge on the host: kept.
- qemu_session.py: a v4 acceptance boot fails without "Stadium: N cells",
  "Stadium conservation: CONSERVED" and the heartbeat's ticks (#189).

Tests first (logs/20261113-122142): the physics check failed on the v4
boot; test_stadium_node, test_stadium_ops (and its share case, after a
real boot showed ";" taking all the heat) failed before. Now: kernel host
tests all pass; amd64 v4 boot passes, POST 539/539, dict_hash unchanged,
"Stadium opcodes: 30 resident, hottest opcode 8", CONSERVED; a system=v3
boot prints its Stadium lines as on 2026-11-06.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

kernel/tests/test_stadium_node.c

@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: LicenseRef-Starship-1.0
+ * Copyright (c) 2023-2026 Robert A. James
+ */
+/* test_stadium_node.c -- kernel/src/vm/stadium.c and session.c on the host (#189, plan
+ * 2026-11-13-engine-step4-phase1, Task 1): the Stadium keyed by a v4 node's number (Captain Bob,
+ * 2026-11-13: "A new node key"). A node's key is none of v3's (not Hera's all-zero, not "none"); the
+ * Stadium can be made with that key in its first quota; the node is born on cell 0, its session
+ * registered and pinned, its whole share in its reservoir -- as Hera is on v3's path, which keeps
+ * vm_uuid_hera() and stadium_birth_hera().
+ *
+ * What the sources call outside themselves is defined here.
+ */
+#include "harness.h"
+#include "starkernel/vm/stadium.h"
+#include "starkernel/session.h"
+#include "starkernel/vm_uuid.h"
+#include "starkernel/kmalloc.h"
+#include "starkernel/q48_16.h"
+#include <stdarg.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+void *kmalloc(size_t size) { return calloc(1, size); }
+void kfree(void *ptr) { free(ptr); }
+kmalloc_stats_t kmalloc_get_stats(void)
+{
+    kmalloc_stats_t s;
+    memset(&s, 0, sizeof s);
+    s.free_bytes = 16u * 1024u * 1024u;          /* a small heap: the Stadium takes its percentage of it */
+    return s;
+}
+void log_message(int level, const char *fmt, ...) { (void)level; (void)fmt; }
+void sk_hal_panic(const char *message) { printf("PANIC: %s\n", message); exit(2); }
+int blk_flush(uint32_t block_num) { (void)block_num; return 0; }
+
+int main(void)
+{
+    VMUuid key = stadium_node_key(10), other = stadium_node_key(11);
+    Session *s;
+
+    CHECK(!vm_uuid_is_hera(key) && !vm_uuid_is_none(key), "a node's key is neither Hera's (all-zero) nor none");
+    CHECK(!vm_uuid_equal(key, other), "two nodes, two keys");
+    CHECK(vm_uuid_equal(key, stadium_node_key(10)), "a node's key is the same each time");
+
+    CHECK(stadium_boot_init_for(key) == 0 && stadium_is_initialized(), "the Stadium is made with the node's key first");
+    CHECK(session_boot_init() == 0, "the sessions");
+    CHECK(stadium_quota_slot_for_vm(key) == 0, "the node holds the first quota");
+    CHECK(stadium_quota_slot_for_vm(vm_uuid_hera()) < 0, "and Hera's all-zero key none");
+    CHECK(stadium_reservoir_peek(key) == Q48_ONE, "its reservoir holds the whole share, 1.0");
+
+    CHECK(stadium_birth_node(key, "Hera") == 0, "the node is born");
+    s = session_find(key);
+    CHECK(s != 0 && s->stadium_cell == 0, "on cell 0, patron zero, its session registered");
+    CHECK(session_is_pinned(key), "and pinned");
+    CHECK(stadium_conserved(key), "conservation holds: resident heat and reservoir sum to 1.0");
+    CHECK(stadium_birth_node(key, "Hera") == 0 && session_find(key) == s, "born twice is born once");
+    return DONE();
+}