Stage G: SEND, and two workers interleave; decision compares work heat (FABRIC-3.8 §3.8, §3.13.7)

SEND ( paddr plen name-c name-u -- ok? ): general kernel-Hermes send to a
named VM, from = calling VM, one block max (refused, not truncated), every
VM. New SK_HERMES_MSG_TYPE_SEND (30).

Ruling C-4 (beta), Captain Bob: the switch decision compares work heat --
the heat each VM pulled in by its own per-beat charges -- not absolute
heat, so Hera's structural endowment no longer makes her hottest. Before
it, the two-worker test ran serial (AAAA...BBBB); after it, byte-identical
on amd64/aarch64/riscv64:
AAABBBBBBBBAAAAAAAABBBBBAAAAABBBBBAAAAABBBBBAAAAABBBBBAAAAABBBBBAAAAABBBBBAAAABB
(40 A, 40 B, 16 runs; ordinary words only, nothing yields). Acceptance:
relay 3, idle growth 0; dict_hash set changed by the new word
(word_count 533) and identical across ISAs.

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

include/starkernel/capsule_vm_switch_signal.h

@@ -138,7 +138,9 @@ int  sk_vm_switch_signal_take_decision_due(void);
  * Among registered participants other than `self` that have work -- a
  * pending kernel-Hermes message, or parked on their own stack mid-task
  * (top frame not VM_FRAME_IDLE), or (Hera only) pending console input --
- * returns the one with the lowest VM-physics heat; among equally cool
+ * returns the one with the lowest work heat (vm_physics_work_heat_of(): heat
+ * earned by its own per-beat charges -- ruling C-4 (β), FABRIC-3.8.md
+ * §3.13.7; Hera's structural endowment doesn't count); among equally cool
  * candidates, the one waiting longest (unique wait stamps). With
  * self_competes set (the caller still has work), returns a candidate only
  * if it is strictly cooler than `self`. Returns NULL when nobody should