openapi: add missing 4xx/5xx response bodies for cloud-emitting endpoints

Vendor declares shared endpoints (e.g. /api/queue, /api/settings,
/api/assets/*, /api/billing/*) with success responses but is missing
many of the 4xx/5xx error response bodies that Comfy-Org/cloud's
runtime actually emits. Cloud's Go handlers reference the generated
ingest.Op<StatusCode>JSONResponse types for these missing statuses,
which currently fail to resolve when codegen runs against the
vendored spec.

This PR adds 237 response entries across 117 operations, restoring
the documented error responses that cloud emits. Bodies are copied
verbatim from Comfy-Org/cloud's hand-written ingest spec
(services/ingest/openapi.yaml) and reference a new ErrorResponse
schema also added in this PR (matches cloud's {code, message} runtime
shape, tagged x-runtime: [cloud]).

ErrorResponse is intentionally separate from the existing CloudError
schema. CloudError's shape ({error}) describes one runtime; cloud
emits a different shape ({code, message}). Existing CloudError refs
in vendor are untouched; new cloud-emitting error references use
ErrorResponse.

Identified via Comfy-Org/cloud's TestCutoverSafe build-safety gate
(BE-1106). Companion to PR #14060 (operationId renames) and PR #14061
(cloud-only schema additions).

.github/workflows/backport_release.yaml

@@ -458,41 +458,6 @@ jobs:
 
           echo "Released ${NEW_VERSION} on ${RELEASE_BRANCH}."
 
-      - name: Delete remote source branch
-        env:
-          GH_TOKEN:        ${{ steps.app-token.outputs.token }}
-          REPO:            ${{ github.repository }}
-          SOURCE_BRANCH:   ${{ steps.resolve.outputs.source_branch }}
-          SOURCE_COMMIT:   ${{ inputs.commit }}
-          RELEASE_BRANCH:  ${{ steps.latest.outputs.release_branch }}
-          DEFAULT_BRANCH:  ${{ github.event.repository.default_branch }}
-        run: |
-          set -euo pipefail
-
-          # Belt-and-braces: the resolve step already refuses the default branch,
-          # but never delete the default or the release branch under any
-          # circumstances.
-          if [[ "${SOURCE_BRANCH}" == "${DEFAULT_BRANCH}" || "${SOURCE_BRANCH}" == "${RELEASE_BRANCH}" ]]; then
-            echo "::error::Refusing to delete '${SOURCE_BRANCH}' (matches default or release branch)."
-            exit 1
-          fi
-
-          # Delete the source branch on origin, but only if its tip is still the
-          # SHA we released from. If someone pushed new commits to it after we
-          # resolved it, leave it alone — those commits would be silently lost.
-          current_tip="$(git ls-remote origin "refs/heads/${SOURCE_BRANCH}" | awk '{print $1}')"
-          if [[ -z "${current_tip}" ]]; then
-            echo "Source branch '${SOURCE_BRANCH}' no longer exists on origin; nothing to delete."
-            exit 0
-          fi
-          if [[ "${current_tip}" != "${SOURCE_COMMIT}" ]]; then
-            echo "::warning::Source branch '${SOURCE_BRANCH}' tip (${current_tip}) no longer matches released commit (${SOURCE_COMMIT}). Leaving it in place."
-            exit 0
-          fi
-
-          git push origin --delete "refs/heads/${SOURCE_BRANCH}"
-          echo "Deleted remote branch '${SOURCE_BRANCH}'."
-
       - name: Summary
         if: always()
         env: