refactor(ci): extract app-discovery output logic into script

Inline shell duplicated across four deploy workflows. Single
source now in scripts/github/output_apps.sh.

scripts/github/output_apps.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# scripts/github/output_apps.sh
+#
+# Resolve the app list and write it to GITHUB_OUTPUT.
+# Inputs via env (forwarded to scripts/meta/resolve/apps.sh):
+#   TEST_DEPLOY_TYPE  — required (server|workstation|universal)
+#   WHITELIST         — optional space-separated allowlist
+set -euo pipefail
+
+apps="$(./scripts/meta/resolve/apps.sh)"
+[[ -n "$apps" ]] || apps='[]'
+
+echo "apps=$apps" >>"$GITHUB_OUTPUT"
+echo "apps_json=$apps" >>"$GITHUB_OUTPUT"
+echo "apps_json=$apps"