ci(mantis): collect discord thread lane artifacts

.github/workflows/mantis-discord-thread-attachment.yml

@@ -330,9 +330,7 @@ jobs:
           run_lane() {
             local lane="$1"
             local repo_root="${GITHUB_WORKSPACE}/${worktree_root}/${lane}"
-            local output_dir="${GITHUB_WORKSPACE}/${root}/${lane}"
-            rm -rf "$output_dir"
-            mkdir -p "$output_dir"
+            local output_dir=".artifacts/qa-e2e/mantis/discord-thread-attachment/${lane}"
             pnpm --dir "$repo_root" openclaw qa discord \
               --repo-root "$repo_root" \
               --output-dir "$output_dir" \
@@ -341,6 +339,9 @@ jobs:
               --credential-role ci \
               --scenario discord-thread-reply-filepath-attachment \
               --allow-failures
+            rm -rf "$root/$lane"
+            mkdir -p "$root/$lane"
+            cp -a "$repo_root/$output_dir/." "$root/$lane/"
           }
 
           run_lane baseline
@@ -415,7 +416,7 @@ jobs:
         with:
           name: mantis-discord-thread-attachment-${{ github.run_id }}-${{ github.run_attempt }}
           path: ${{ steps.run_mantis.outputs.output_dir }}
-          if-no-files-found: error
+          if-no-files-found: warn
           retention-days: 14
 
       - name: Create Mantis GitHub App token
@@ -443,6 +444,10 @@ jobs:
           set -euo pipefail
 
           root=".artifacts/qa-e2e/mantis/discord-thread-attachment"
+          if [[ ! -f "$root/mantis-evidence.json" ]]; then
+            echo "No Mantis evidence manifest found; skipping PR evidence comment."
+            exit 0
+          fi
           artifact_url_args=()
           if [[ -n "${ARTIFACT_URL:-}" ]]; then
             artifact_url_args=(--artifact-url "$ARTIFACT_URL")