fix(ci): reclaim space for semantic backup smoke

scripts/unified-deployment-smoke.sh

@@ -2469,12 +2469,14 @@ task13_self_test_registry_fingerprint() {
 
 task13_self_test_source_contract() {
   local root host_network push_command registry_function workflow uses_count pinned_uses_count
+  local runner_preparation path
   local auth_runtime_mount auth_root_mount auth_projection auth_runtime_owner
   local pi_auth_bind pi_projection registry_runtime_mount registry_root_mount registry_projection
   local application_secret_bind application_secret_mount application_secret_projection
   local application_secret_parent_owner application_secret_file_owner
   root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd -P)"
   workflow="$root/.github/workflows/deployment.yml"
+  runner_preparation="$root/scripts/prepare-linux-docker-runner.sh"
   host_network='--network'' host'
   push_command='docker image ''push'
   registry_function='task13_start_''registry'
@@ -2543,6 +2545,16 @@ task13_self_test_source_contract() {
     || task13_fail "CI lacks an outer timeout for the unified deployment smoke"
   grep -Eq 'timeout .*scripts/tht-update-smoke\.sh' "$workflow" \
     || task13_fail "CI lacks an outer timeout for the tht update smoke"
+  grep -Fq 'bash scripts/prepare-linux-docker-runner.sh' "$workflow" \
+    || task13_fail "CI must reclaim unused hosted-runner toolchains before the Docker release smoke"
+  [[ -x "$runner_preparation" ]] \
+    || task13_fail "the Linux Docker runner preparation must be executable"
+  for path in /usr/local/lib/android /usr/share/dotnet /opt/ghc /usr/local/.ghcup; do
+    grep -Fq -- "$path" "$runner_preparation" \
+      || task13_fail "the Linux Docker runner preparation is missing the scoped path: $path"
+  done
+  ! grep -Eq '/opt/hostedtoolcache([/[:space:]]|$)|rm[[:space:]]+-rf[[:space:]]+--?[[:space:]]+/($|[[:space:]])' "$runner_preparation" \
+    || task13_fail "the Linux Docker runner preparation must not remove required tool caches or broad roots"
   uses_count="$(grep -Ec '^[[:space:]]+uses:' "$workflow")"
   pinned_uses_count="$(grep -Ec '^[[:space:]]+uses: [^[:space:]]+@[0-9a-f]{40}([[:space:]]|$)' "$workflow")"
   [[ "$uses_count" -gt 0 && "$uses_count" -eq "$pinned_uses_count" ]] \