Add Cloud Agent development environment config

.cursor/environment.json

@@ -0,0 +1,11 @@
+{
+  "name": "Cathedral SN39",
+  "install": "bash .cursor/install.sh",
+  "terminals": [
+    {
+      "name": "publisher",
+      "command": "source .venv/bin/activate && CATHEDRAL_DB_PATH=/tmp/publisher.db PORT=8000 uvicorn scaffold.publisher.server:app --host 0.0.0.0 --port 8000"
+    }
+  ],
+  "ports": [{ "name": "publisher", "port": 8000 }]
+}

.cursor/install.sh

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+#!/usr/bin/env bash
+# Idempotent Cloud Agent bootstrap for the Cathedral SN39 repository.
+#
+# Sets up an isolated virtualenv with the thin-subnet mechanism/test toolchain
+# (matches .github/workflows/required-checks.yml) plus the two extra runtime
+# deps the SQLite-backed publisher server needs (multipart form parsing and
+# canonical blake3 hashing). Safe to run repeatedly.
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$repo_root"
+
+# Cursor's default image ships Python 3.12 but omits the venv seed package, so
+# `python3 -m venv` fails with an ensurepip error until it is installed.
+if ! python3 -c "import ensurepip" >/dev/null 2>&1; then
+  sudo apt-get update -qq
+  sudo apt-get install -y -qq python3.12-venv
+fi
+
+if [ ! -x .venv/bin/python ]; then
+  python3 -m venv .venv
+fi
+
+# shellcheck disable=SC1091
+. .venv/bin/activate
+
+python -m pip install --upgrade pip
+
+# Core mechanism + reviewed test/lint toolchain (`.[test]`) matches CI. The two
+# trailing deps are the publisher runtime essentials for the default SQLite
+# backend; Postgres (psycopg2) and S3 (boto3) stay optional and load lazily.
+python -m pip install -e '.[test]' 'python-multipart>=0.0.9' 'blake3>=1.0'
+
+echo "Cathedral dev environment ready: $(.venv/bin/python --version)"