feat(v4): the mesh boot to spec -- Hera born empty in the kernel's fabric; births, kills, every node stepping together (#189)

ENGINE step 4 Phase 1, Tasks 5b-5d, and the edge cases (Captain Bob, 2026-11-13: "Build it to proper
spec"; "Check for the edge cases"; "Yes, add it to v4-checks").

- v4/system/mesh.c, v4/include/v4/mesh.h: the nucleus assembled by the ROM and given to Hera as F18
  cells; Hera born empty at place 0, the kernel on port 0, the console on port 1; told she is 10, in the
  registry, the kernel's words, FORTH-79, sealed, POST, the kernel's capsules. NODE-BORN / NODE-KILL in
  the owner's room.
- No scheduler: v4_mesh_tell returns once the node told says how its text ended, and
  v4_mesh_step / v4_mesh_busy let the host step the fabric while it waits, so nodes run between
  lines as during them. A text left "waiting" is owed its end: the next line ends it "Interrupted"
  and is then run (MESH.md 7b.6).
- kernel: sk_v4.c boots through the mesh; its idle steps the fabric while a node can run, and halts
  only when none can (#151 kept). stadium_return_quota and stadium_ops_forget on a kill.
- Tests: v4/tests/test_mesh_boot.c (32 checks: the boot, births, kills, rebirth, a live number, a
  fault, no such node, Hera not killing herself, no room, a line too long, a node running for ever,
  a wait broken by the next line), run by `make -C v4 test` and under ASan+UBSan by `sanitize`
  (v4-checks); kernel/tests quota return; scripts/qemu_session.py births() and the edges on bare
  metal.
- Docs: ENGINE.md 6 "who runs next" struck (settled: no scheduler); the Phase 1 plan; FABRIC-3
  XLVIII.23; .claude/memory/rules.md: alpha.5 closed to new work.
- Evidence: v4-checks 80 programs under the sanitizers, 0 failures; the hosted builds alike; two
  stopped v4-checks runs labelled STOPPED; three development amd64 boots labelled.

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

kernel/tests/test_stadium_ops.c

@@ -86,5 +86,23 @@ int main(void)
         CHECK(h5 > 2u * h0 && h5 < 4u * h0, "in proportion to their retirements, about 3 to 1");
         CHECK(stadium_reservoir_peek(k2) >= Q48_ONE / 3 && stadium_conserved(k2), "the floor kept, conservation held");
     }
+
+    /* a node killed: its quota given back (#189, Phase 1 Task 5c) -- its patrons evicted, its cells
+     * to the node it came from, its slot free for the next birth; its opcode counts forgotten */
+    {
+        VMUuid k2 = stadium_node_key(12), k3 = stadium_node_key(13);
+        uint64_t c3[32];
+        stadium_ops_forget(k2);
+        CHECK(stadium_return_quota(k2, key) == 0, "node 12's quota is given back to node 10");
+        CHECK(stadium_quota_slot_for_vm(k2) < 0 && stadium_ops_heat(k2, 5) == 0, "node 12 has no quota, and no opcode heat");
+        CHECK(stadium_conserved(key), "node 10 conserved after taking its cells back");
+        CHECK(stadium_return_quota(key, key) != 0 && stadium_return_quota(k2, key) != 0, "a quota is not given back to itself, or twice");
+        CHECK(stadium_grant_quota(k3, key) == 0, "the slot is free: node 13 is granted one");
+        memset(c3, 0, sizeof c3);
+        c3[7] = 2;
+        stadium_ops_charge(k3, c3, 30);
+        CHECK(stadium_ops_heat(k3, 7) == 2u * (uint64_t)STADIUM_WORD_HEAT_QUANTUM && stadium_ops_heat(k3, 5) == 0,
+              "node 13 starts with no counts of node 12's: two retirements, two quanta");
+    }
     return DONE();
 }