§H.12 step 20: CH-REQUEST initiator-only gate (MY-CH-ID)

Added VARIABLE MY-CH-ID to messaging.4th (fail-closed -1 default) and
set it per-VM in hermes/init.4th and artemis/init.4th. CH-REQUEST now
refuses if the caller-supplied 'from' doesn't match the calling VM's
own id, closing a real spoofing gap found while implementing this.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QgooKd5hJNtTYqB6CyK5f9

capsules/artemis/init.4th

@@ -497,5 +497,6 @@ Block 4854
 ( INIT). Hermes always exists by Artemis's birth. )
 S" common:messaging.4th" EXEC
 MSG-CD-INIT
+2 MY-CH-ID !
 S" 2 COMMON-CH @ CH-ADD-MBR" S" Hermes" VM-EXEC
 STARTUP-BANNER