S00-011: Verify public npm access and exact-version tarball integrity

Changes: Add a scoped fresh-cache registry probe, safe reproduction instructions and artifact ignore rule; record actual TLS-enabled metadata/download results and review handoff without selecting a stack or changing the harness.
Validation: Original npm view command and verify.py returned exit 0; react@19.3.1 tarball (26394 bytes) matched registry SHA-512. make check passed validation and 66 tooling tests. git diff --check passed. App install/build and different-harness connectivity remain unverified.

Task: S00-011
Agent: auto-ci-cd-d105e8027730
Role: ci-cd
Action: claim
Status: review

Task title: Restore verified npm registry access for the stack spike

experiments/0001-stack/registry-access/verify.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+"""Fetch public npm metadata/tarball without installing or running package code."""
+import base64
+import hashlib
+import json
+import os
+from pathlib import Path
+import subprocess
+import tempfile
+
+
+ROOT = Path(__file__).resolve().parent
+PACKAGE = "react@19.3.1"  # Connectivity sample only; not a stack decision.
+
+
+def main():
+    if os.environ.get("NODE_TLS_REJECT_UNAUTHORIZED") == "0":
+        raise SystemExit("Refusing disabled Node TLS verification")
+    artifacts = ROOT / "artifacts"
+    artifacts.mkdir(exist_ok=True)
+    # Empty configuration files prevent inherited npm credentials/config from
+    # being needed for this public probe. Never print the process environment.
+    with tempfile.TemporaryDirectory(prefix="luma-registry-", dir="/private/tmp") as temp:
+        temp = Path(temp)
+        for name in ("user.npmrc", "global.npmrc"):
+            (temp / name).write_text("", encoding="utf-8")
+        common = [
+            "--registry=https://registry.npmjs.org/", "--strict-ssl=true",
+            "--fetch-retries=0", "--fetch-timeout=15000",
+            f"--cache={temp / 'cache'}", f"--userconfig={temp / 'user.npmrc'}",
+            f"--globalconfig={temp / 'global.npmrc'}",
+        ]
+
+        def npm(args):
+            # Run outside the project so no project .npmrc is inherited.
+            result = subprocess.run(["npm", *args, *common], cwd=temp,
+                                    check=True, capture_output=True, text=True,
+                                    timeout=60)
+            print("npm " + " ".join(args) + " [isolated TLS/cache options]: exit 0")
+            return json.loads(result.stdout)
+
+        metadata = npm(["view", PACKAGE, "version", "license", "engines", "dist", "--json"])
+        if metadata["version"] != "19.3.1":
+            raise SystemExit("Unexpected package version")
+        if metadata["dist"]["tarball"] != "https://registry.npmjs.org/react/-/react-19.3.1.tgz":
+            raise SystemExit("Unexpected tarball origin/path")
+        integrity = metadata["dist"]["integrity"]
+        algorithm, expected = integrity.split("-", 1)
+        if algorithm != "sha512":
+            raise SystemExit("Expected SHA-512 registry integrity")
+        base64.b64decode(expected, validate=True)
+        packed = npm(["pack", PACKAGE, "--ignore-scripts", "--json",
+                      f"--pack-destination={artifacts}"])
+        if len(packed) != 1 or packed[0]["filename"] != "react-19.3.1.tgz":
+            raise SystemExit("Unexpected pack output")
+        tarball = artifacts / "react-19.3.1.tgz"
+        actual = "sha512-" + base64.b64encode(hashlib.sha512(tarball.read_bytes()).digest()).decode("ascii")
+        if actual != integrity or packed[0]["integrity"] != integrity:
+            raise SystemExit("Tarball integrity mismatch")
+        (artifacts / "metadata.json").write_text(json.dumps(metadata, indent=2) + "\n", encoding="utf-8")
+        result = {"package": PACKAGE, "bytes": tarball.stat().st_size,
+                  "integrity": actual, "registry_integrity_match": True}
+        print(json.dumps(result, indent=2))
+        (artifacts / "result.json").write_text(json.dumps(result, indent=2) + "\n", encoding="utf-8")
+
+
+if __name__ == "__main__":
+    main()