feat(scrape): operator proof script and podman-compose smoke fix

Add run-operator-proof for one-target handoff/scrape/prove flows.
Prefer podman-compose on Podman hosts but honor DCE_DOCKER_BIN overrides
so offline smokes keep using fake compose shims.

scripts/tests/run-operator-proof-smoke.sh

@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+
+set -Eeuo pipefail
+
+REPO_ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd -P)
+PROOF="$REPO_ROOT/scripts/run-operator-proof.sh"
+TMP_DIR=$(mktemp -d "${TMPDIR:-/tmp}/dce-operator-proof-smoke.XXXXXX")
+CONFIG_PATH="$TMP_DIR/config.json"
+ENV_PATH="$TMP_DIR/scrape.env"
+
+cleanup() {
+  rm -rf "$TMP_DIR"
+}
+trap cleanup EXIT
+
+mkdir -p "$TMP_DIR/archive/demo"
+printf '{"messages":[{"id":"1"}],"channel":{"id":"111111111111111111"}}\n' \
+  >"$TMP_DIR/archive/demo/Guild - general [111111111111111111].json"
+
+cat >"$CONFIG_PATH" <<JSON
+{
+  "archive_root": "$TMP_DIR/archive",
+  "targets": [
+    {
+      "name": "demo",
+      "kind": "guild",
+      "output_dir": "$TMP_DIR/archive/demo",
+      "channel_ids": ["111111111111111111"],
+      "enabled": true
+    }
+  ]
+}
+JSON
+
+printf 'DISCORD_TOKEN=dummy\n' >"$ENV_PATH"
+
+set +e
+output=$(
+  DCE_MIN_FREE_MB=0 \
+    DCE_CONFIG_FILE="$CONFIG_PATH" \
+    DCE_ENV_FILE="$ENV_PATH" \
+    "$PROOF" --config "$CONFIG_PATH" --target demo --dry-run 2>&1
+)
+status=$?
+set -e
+
+if [[ "$status" -ne 0 ]] || ! grep -q 'Dry run complete' <<<"$output"; then
+  printf 'run-operator-proof dry-run failed (status=%s)\n' "$status" >&2
+  printf '%s\n' "$output" >&2
+  exit 1
+fi
+
+printf 'run-operator-proof-smoke: ok\n'