fix(ha): add DRBD sync progress indicator and pre-flight sync gate

cluster-init.sh: replace the fixed 300-iteration sync wait with an
indefinite loop that prints an in-place progress line (%done, ETA, speed)
from /proc/drbd every 3 s. Clears the line with printf \r before logging
completion, so the output stays clean alongside the [cluster-init] log
lines.

acceptance-tests.sh: add a pre-flight check that hard-exits if
drbdadm dstate is not UpToDate/UpToDate, with a hint to the watch
command for monitoring progress. Tests cannot give accurate results
while the initial full-sync is in progress.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/ha/acceptance-tests.sh

@@ -34,6 +34,25 @@ echo "════════════════════════
 echo " HA Cluster Acceptance Tests — $(date '+%Y-%m-%d %H:%M:%S')"
 echo "════════════════════════════════════════════════════"
 
+# ── Pre-flight: DRBD sync must be complete ────────────────────────────────
+# Tests that check disk state, XFS mount, and iSCSI will fail or give false
+# results while the initial full sync is in progress.  Block until done.
+echo ""
+echo "Pre-flight: verifying DRBD sync is complete..."
+DRBD_PREFLIGHT=$(n1 "drbdadm dstate ha-data 2>/dev/null" 2>/dev/null || echo "unknown")
+if ! echo "$DRBD_PREFLIGHT" | grep -q "^UpToDate/UpToDate$"; then
+  echo ""
+  echo "  ERROR: DRBD initial sync not complete."
+  echo "  Current dstate on $NODE1: $DRBD_PREFLIGHT"
+  echo ""
+  echo "  Monitor progress:"
+  echo "    ssh nixos@$NODE1_IP 'sudo watch -n3 cat /proc/drbd'"
+  echo ""
+  echo "  Re-run this script once dstate shows UpToDate/UpToDate."
+  exit 1
+fi
+echo "  dstate: $DRBD_PREFLIGHT — ready."
+
 # ── Detect Active/Standby nodes ────────────────────────────────────────────
 # Use crm_mon to detect which node holds the Promoted (Primary) DRBD resource.
 # Pacemaker is authoritative; DRBD role can briefly read as Secondary while