Stage H: DoE rebuilt on BIRTH/SEND/KILL, defs-only workloads; work heat floor on contact (FABRIC-3.8 §3.9, §3.13.7)

Workload capsules the DoE births are definitions only; each defines WL-RUN
(its old birth-time work plus its entry word twice) and WL-DONE-ARGS. The
driver births N workers, SENDs each 'WL-RUN WL-DONE-ARGS SEND', waits in an
ordinary loop for N MU-DONE messages, KILLs them (parked idle), and emits
the marker. The serialized VM-EXEC round-robin is gone.

Kernel: no switch checkpoint after a payload's last word; work heat is the
assessed per-beat charge, and a VM gaining work is raised to the busy set's
floor (Captain Bob's ruling) -- fixes a live stall where a busy-waiting Hera
never yielded, without serializing batch starts.

Evidence: cfg-4 rows spread evenly over Hera and all 8 worker slots (44k
switches); full cfg-4 trials on amd64/aarch64/riscv64 end fail=0 with 8/8
KILL dead; Stage G interleave byte-identical on all three. Acceptance:
dict_hash unchanged, relay 3, idle growth 0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

include/starkernel/capsule_vm_switch_signal.h

@@ -150,6 +150,15 @@ int  sk_vm_switch_signal_take_decision_due(void);
  */
 struct VM *sk_vm_switch_decide(struct VM *self, int self_competes);
 
+/* Stage H, "floor on contact" (Captain Bob, 2026-09-23): vm_id just gained
+ * work (kernel_hermes.c: its queue went from empty to one message). If it
+ * had none before -- not running, not parked mid-task -- raise its work
+ * heat to the lowest work heat among the VMs that have work now (the one
+ * running and every eligible participant). A new or long-idle VM thus
+ * joins the busy set level with its floor, rather than at 0 and running
+ * alone until it "caught up" with VMs that have worked since boot. */
+void sk_vm_switch_signal_note_work_gained(VMUuid vm_id);
+
 /* Reap one participant marked pending_reap (a WIREBIND identity whose
  * device detached while it was parked), if any. Call only at a safe point
  * (checkpoint, trampoline, idle point) -- same contract the old Stage 3