review: iteration-3 fixes (convergence pass)

- ci-cd.md phrasing made time-invariant (true before and after the
  visibility flip; the prior wording asserted a state not yet real).
- ui-shot: liveness check before the tap QMP call too — the commit-message
  claim of "before every QMP call" is now actually true.
- busybox fetcher checks its pin before downloading, mirroring the
  kernel-tarball fetcher's ordering.
- Fragment disable-arm: absence of a deps-gated symbol is a valid disable
  outcome; only "still set" is fatal (the iteration-2 symmetrization
  overcorrected). Negative-tested both directions under set -e.

Iteration 3 produced four findings, none blocking, all applied — the
recursive review is converged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018HUayid7W5w7jBdb9Rrj1K

qemu/tests/ui-shot.sh

@@ -123,6 +123,7 @@ done
 # Tap the "Metrics" tab: pixel (373,40) of 720x720 scaled to the QMP absolute
 # range 0..32767 — switching tabs must repaint the content area. Poll for the
 # repaint rather than guessing a delay.
+vm_alive_or_die
 qmp tap 16975 1820
 changed=0
 # 90s, matching the first-frame budget: TCG repaints are CPU-bound and a