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

scripts/qemu_session.py

@@ -478,6 +478,15 @@ def del_zuse(n):
     qcmd("blockdev-del", **{"node-name": f"zuse{n}"})
 
 
+def physics():
+    """A v4 boot's physics, before its prompt (#189: "a boot without the physics fails"; plan
+    2026-11-13-engine-step4-phase1, Task 4): the Stadium made, conservation checked, the heartbeat
+    ticking.  A v3 boot prints the same lines (kernel_main.c, stadium_words.c)."""
+    check("the Stadium: its cells allocated", re.search(r"Stadium: \d+ cells", text()) is not None)
+    check("the Stadium: conservation CONSERVED", wait_for(r"Stadium conservation: CONSERVED", 120))
+    check("the heartbeat: ticking", wait_for(r"Heartbeat: [1-9]\d* ticks", 120))
+
+
 check("POST: PASSED", wait_for(r"POST: PASSED", 900))
 m = a.mode
 
@@ -489,6 +498,7 @@ elif m == "zuse":
           re.search(r"Boot disk: not a StarshipOS stick", text()) is not None, near=r"Boot successful!")
     check("Zuse: genesis minted onto attached thumbdrive (a fresh data stick)",
           wait_for(r"Zuse: genesis minted onto attached thumbdrive", 180), near=r"Artemis: |Zuse: |USB: ")
+    physics()
     check("[zuse@Hera] ok>", wait_for(PROMPT, 60))
     n = count(PROMPT)
     type_line("3 4 + .")
@@ -559,6 +569,7 @@ elif m in ("genesis", "stick_genesis"):
               near=r"Boot successful!")
     check("Zuse: genesis minted onto attached thumbdrive",
           wait_for(r"Zuse: genesis minted onto attached thumbdrive", 180), near=r"Artemis: |Zuse: ")
+    physics()
     check("[zuse@Hera] ok>", wait_for(PROMPT, 60))
     check("no identity confirmed on a first boot", count(r"Zuse: identity confirmed") == 0)
     n = count(PROMPT)