ci(spark): adopt estate SPARK Theatre Gate (standards#135)

Thin caller of the reusable hyperpolymath/standards SPARK Theatre Gate,
pinned to the #141 merge commit 462003782f3ebb93ea763e81d0d199ce13ef7d73 per the estate action-pinning
policy. Makes the anti-theatre enforcement live in this repo.

Refs hyperpolymath/standards#124
Refs hyperpolymath/standards#135

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/spark-theatre-gate.yml

@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: PMPL-1.0
+# Estate SPARK Theatre Gate — thin caller of the reusable workflow in
+# hyperpolymath/standards (#135 / #141). Pinned by commit SHA per the
+# estate action-pinning policy. Regenerate the pin only when the reusable
+# workflow is intentionally bumped.
+name: SPARK Theatre Gate
+
+on:
+  pull_request:
+  push:
+    branches: [main, master]
+
+permissions:
+  contents: read
+
+jobs:
+  spark-theatre-gate:
+    uses: hyperpolymath/standards/.github/workflows/spark-theatre-gate.yml@462003782f3ebb93ea763e81d0d199ce13ef7d73
+    with:
+      paths: "."
+      enforce_zero_contract: false