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/include/starkernel/vm/stadium.h

@@ -195,6 +195,16 @@ VMUuid stadium_node_key(uint32_t node);
 int    stadium_boot_init_for(VMUuid first);
 int    stadium_birth_node(VMUuid key, const char *name);
 
+/*
+ * stadium_return_quota(vm, to) -- a node is gone: its quota is given back (#189, Phase 1 Task 5c),
+ * the inverse of stadium_grant_quota(). Every resident patron of it is evicted, its heat cooling to
+ * its reservoir as any eviction's does; its free cells go to `to`'s free list; its slot is free for
+ * the next grant. Its reservoir -- the share of 1.0 its grant gave it, its own -- goes with it, as
+ * the grant made it. 0, or -1: no such quota, `to` none or the same, the first quota (patron zero's),
+ * or a patron that cannot be evicted (pinned, or holding another).
+ */
+int    stadium_return_quota(VMUuid vm_id, VMUuid to_vm_id);
+
 /* stadium_is_initialized - Whether stadium_boot_init() has succeeded. */
 int stadium_is_initialized(void);
 

kernel/include/starkernel/vm/stadium_ops.h

@@ -38,6 +38,10 @@ void stadium_ops_init(void);
  * `tick` the heartbeat's count now. Nothing for a key with no quota. */
 void stadium_ops_charge(VMUuid vm_id, const uint64_t counts[STADIUM_OPS_COUNT], uint64_t tick);
 
+/* A node is gone: its opcode counts are forgotten, so a node that later has its quota's slot starts
+ * from none (#189). Before stadium_return_quota(), while the key still has its slot. */
+void stadium_ops_forget(VMUuid vm_id);
+
 /* An opcode patron's heat now (Q48.16), or 0: not resident, or no quota. */
 uint64_t stadium_ops_heat(VMUuid vm_id, unsigned op);