feat(jobs): add resumable preprocessing envelope

harness/tests/test_job_locking.py

@@ -0,0 +1,61 @@
+import multiprocessing
+from pathlib import Path
+
+import pytest
+
+from tht.jobs.locking import JobAlreadyRunningError, WorkspaceJobLock
+
+
+def _hold_lock(root: str, ready, release):
+    with WorkspaceJobLock(Path(root), "demo", "evidence"):
+        ready.set()
+        release.wait(10)
+
+
+def _crash_with_lock(root: str, ready):
+    lock = WorkspaceJobLock(Path(root), "demo", "evidence")
+    lock.acquire()
+    ready.set()
+    raise SystemExit(7)
+
+
+def test_same_workspace_and_job_are_exclusive_across_processes(tmp_path):
+    context = multiprocessing.get_context("spawn")
+    ready = context.Event()
+    release = context.Event()
+    process = context.Process(target=_hold_lock, args=(str(tmp_path), ready, release))
+    process.start()
+    assert ready.wait(10)
+    try:
+        with pytest.raises(JobAlreadyRunningError):
+            WorkspaceJobLock(tmp_path, "demo", "evidence").acquire()
+    finally:
+        release.set()
+        process.join(10)
+    assert process.exitcode == 0
+
+
+def test_evidence_and_dwh_jobs_have_distinct_locks(tmp_path):
+    with WorkspaceJobLock(tmp_path, "demo", "evidence"):
+        with WorkspaceJobLock(tmp_path, "demo", "dwh"):
+            pass
+
+
+def test_lock_keys_cannot_escape_lock_directory(tmp_path):
+    with pytest.raises(ValueError, match="filesystem-safe"):
+        WorkspaceJobLock(tmp_path, "demo", "../evidence")
+
+
+def test_lock_is_recoverable_after_process_crash_without_stale_deletion(tmp_path):
+    context = multiprocessing.get_context("spawn")
+    ready = context.Event()
+    process = context.Process(target=_crash_with_lock, args=(str(tmp_path), ready))
+    process.start()
+    assert ready.wait(10)
+    process.join(10)
+    assert process.exitcode == 7
+
+    lock_path = WorkspaceJobLock(tmp_path, "demo", "evidence").path
+    assert lock_path.exists()
+    with WorkspaceJobLock(tmp_path, "demo", "evidence"):
+        assert lock_path.exists()