FABRIC.md: mark 4.3.x as an open-ended, appendable sublist

Visual cue between 4.3.4 and 4.4 so it's clear at a glance where the
growing 4.3.x Console slice ends and 4.4 begins, without reusing the
document's --- convention (reserved for ## section breaks).

FABRIC.md

@@ -3671,6 +3671,10 @@ document and committing that amendment as its own item.*
   projection machinery. Stop and review here before scoping the next 4.3.x item — not
   expected to be fast. *Refs:* §27.4.
 
+  ⋯ *(4.3.x is open-ended — more items get appended here as Console work is scoped item by*
+  *item, developed on the fly per §25.0. 4.4 below is unaffected by anything added above*
+  *this marker.)*
+
 - [ ] **4.4 — Artemis last.** It works today; it is the thing that cannot be broken.
   *Refs:* §10.