fix(agent99): normalize empty preflight blockers

scripts/reboot-recovery/agent99-remote-atomic-deploy-receiver.ps1

@@ -259,12 +259,13 @@ function Invoke-AgentLivePreflight {
     try { $payload = $match.Groups["json"].Value | ConvertFrom-Json } catch { $payload = $null }
   }
   $summary = if ($payload -and $payload.PSObject.Properties["summary"]) { $payload.summary } else { $null }
-  [string[]]$blockingReasons = if ($processResult.timedOut) {
-    @("preflight_process_timeout")
-  } elseif ($summary) {
-    @($summary.blockingReasons | ForEach-Object { [string]$_ })
-  } else {
-    @("preflight_output_unparseable")
+  [string[]]$blockingReasons = @()
+  if ($processResult.timedOut) {
+    $blockingReasons = @("preflight_process_timeout")
+  } elseif (-not $summary) {
+    $blockingReasons = @("preflight_output_unparseable")
+  } elseif ($null -ne $summary.blockingReasons) {
+    $blockingReasons = @($summary.blockingReasons | ForEach-Object { [string]$_ })
   }
   [string[]]$externalBlockingReasons = @($blockingReasons | Where-Object { $_ -eq "self_health_not_ok" })
   [string[]]$runtimePlaneBlockingReasons = @($blockingReasons | Where-Object { $_ -ne "self_health_not_ok" })

scripts/reboot-recovery/tests/test_agent99_remote_atomic_deploy_transport_contract.py

@@ -502,6 +502,9 @@ def test_receiver_scopes_deploy_health_separately_from_external_asset_health() -
     assert '[int]$summary.alertRunningCount -eq 0' in preflight
     assert '[int]$summary.pendingCommandCount -eq 0' in preflight
     assert '$runtimePlaneBlockingReasons.Count -eq 0' in preflight
+    assert '[string[]]$blockingReasons = @()' in preflight
+    assert '$null -ne $summary.blockingReasons' in preflight
+    assert '$summary.blockingReasons | ForEach-Object' in preflight
     assert 'externalDegraded = [bool](' in preflight