test(P02): attestations dir scaffolded + empty (REQ-331, backend-engineer)

---ci---
project: acdl
phase: 2
milestone: v1.28
status: execute
persona: backend-engineer
---
tests/test_init_attestations.py: nova init in a tmp_path creates
.nova/contract.yml.attestations/ as an empty directory (listdir == []).
The existing test_cli_subcommands.py asserts is_dir() but not emptiness;
this is the explicit REQ-331 assertion (freshly scaffolded repo has no
attestations yet — they are produced later by nova apply --sign-local-review
/ the JWS attestation flow, REQ-332).

tests/test_init_attestations.py

@@ -0,0 +1,50 @@
+"""REQ-331 test: nova init scaffolds .nova/contract.yml.attestations/ empty.
+
+P1 (nova/init.py + core/init_scaffold.py) creates the attestations dir
+during `nova init`. This test explicitly verifies (a) the dir exists and
+(b) it is EMPTY after init (listdir returns []) — a freshly scaffolded
+repo has no attestations yet (they are produced later by
+nova apply --sign-local-review / the JWS attestation flow, REQ-332).
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+
+def _nova_help_cmd():
+    """Return the command list to invoke `nova --help` (prefer installed entry)."""
+    nova = os.path.join(os.path.dirname(sys.executable), "nova")
+    if os.path.isfile(nova):
+        return [nova, "--help"]
+    return [sys.executable, "-m", "nova.cli", "--help"]
+
+
+def test_init_attestations_dir_exists_and_is_empty(tmp_path):
+    """nova init creates .nova/contract.yml.attestations/ and it is empty."""
+    cmd = _nova_help_cmd()
+    init_cmd = cmd[:-1] + ["init"]
+    proc = subprocess.run(init_cmd, capture_output=True, text=True, cwd=str(tmp_path))
+    assert proc.returncode == 0, f"nova init failed: {proc.stderr}"
+    attest_dir = tmp_path / ".nova" / "contract.yml.attestations"
+    assert attest_dir.is_dir(), ".nova/contract.yml.attestations/ not created"
+    # REQ-331: the dir is empty after init (no attestations yet).
+    entries = os.listdir(attest_dir)
+    assert entries == [], (
+        f".nova/contract.yml.attestations/ not empty after init: {entries}"
+    )
+
+
+def test_init_attestations_dir_is_a_directory_not_a_file(tmp_path):
+    """The attestations path is a directory (not a file), so attestation
+    JWS files can be written into it later (REQ-332 flow)."""
+    cmd = _nova_help_cmd()
+    init_cmd = cmd[:-1] + ["init"]
+    proc = subprocess.run(init_cmd, capture_output=True, text=True, cwd=str(tmp_path))
+    assert proc.returncode == 0, f"nova init failed: {proc.stderr}"
+    attest_path = tmp_path / ".nova" / "contract.yml.attestations"
+    assert attest_path.is_dir(), f"{attest_path} is not a directory"
+    assert not attest_path.is_file(), f"{attest_path} is a file, not a directory"