fix: revert ADR edits and enforce immutable accepted records

Restore docs/adr to main; add check_adrs.py CI gate so existing ADR-*.md
files cannot be modified — supersede with a new numbered ADR instead.

simulator/tests/test_check_adrs.py

@@ -0,0 +1,70 @@
+"""Tests for scripts/check_adrs.py — ADR immutability gate."""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+SCRIPTS = Path(__file__).resolve().parents[2] / "scripts"
+sys.path.insert(0, str(SCRIPTS))
+
+from check_adrs import find_modified_adrs, run_check  # noqa: E402
+
+
+def _git(cwd: Path, *args: str) -> None:
+    subprocess.check_call(["git", *args], cwd=cwd, stdout=subprocess.DEVNULL)
+
+
+def test_no_modified_adrs_on_current_branch() -> None:
+    assert run_check(base="origin/main") == 0
+
+
+def test_detects_adr_edit_in_sandbox(tmp_path: Path) -> None:
+    _git(tmp_path, "init")
+    _git(tmp_path, "config", "user.email", "ci@test")
+    _git(tmp_path, "config", "user.name", "ci")
+    adr = tmp_path / "docs/adr"
+    adr.mkdir(parents=True)
+    (adr / "ADR-0001-test.md").write_text("v1\n")
+    _git(tmp_path, "add", ".")
+    _git(tmp_path, "commit", "-m", "add adr")
+    _git(tmp_path, "branch", "-M", "main")
+    (adr / "ADR-0001-test.md").write_text("v2\n")
+    _git(tmp_path, "checkout", "-b", "feature")
+    _git(tmp_path, "add", ".")
+    _git(tmp_path, "commit", "-m", "edit adr")
+
+    monkeypatch = pytest.MonkeyPatch()
+    monkeypatch.setattr("check_adrs.ROOT", tmp_path)
+    try:
+        assert find_modified_adrs("main") == ["docs/adr/ADR-0001-test.md"]
+        assert run_check(base="main") == 1
+    finally:
+        monkeypatch.undo()
+
+
+def test_new_adr_allowed(tmp_path: Path) -> None:
+    _git(tmp_path, "init")
+    _git(tmp_path, "config", "user.email", "ci@test")
+    _git(tmp_path, "config", "user.name", "ci")
+    adr = tmp_path / "docs/adr"
+    adr.mkdir(parents=True)
+    (adr / "ADR-0001-test.md").write_text("v1\n")
+    _git(tmp_path, "add", ".")
+    _git(tmp_path, "commit", "-m", "add adr")
+    _git(tmp_path, "branch", "-M", "main")
+    (adr / "ADR-0002-new.md").write_text("new\n")
+    _git(tmp_path, "checkout", "-b", "feature")
+    _git(tmp_path, "add", ".")
+    _git(tmp_path, "commit", "-m", "add adr 2")
+
+    monkeypatch = pytest.MonkeyPatch()
+    monkeypatch.setattr("check_adrs.ROOT", tmp_path)
+    try:
+        assert find_modified_adrs("main") == []
+        assert run_check(base="main") == 0
+    finally:
+        monkeypatch.undo()