feat(devkit): add resumable workspace automation and UI review tooling

Verified with the coordinated workspace changes by devkit full run
2026-09-08T225814-186389-0000-3e3ed7cd (all seven phases passed).
This shared UI pass does not mark the individual module reviews complete.

tests/test_devkit_cancellation.py

@@ -0,0 +1,88 @@
+"""Signals during snapshot probes must not become passing run evidence."""
+
+import os
+import signal
+
+import pytest
+
+import test_devkit_runner as fixtures
+from govoplan_devkit import runner
+from govoplan_devkit.checkpoints import Checkpoints
+
+example = fixtures.example
+
+
+@pytest.mark.parametrize("interruption", [signal.SIGINT, signal.SIGTERM])
+@pytest.mark.parametrize("probe", ["source", "environment"])
+def test_interrupt_during_final_snapshot_is_not_a_passing_run(
+    example, monkeypatch, interruption, probe
+):
+    args, repo = example
+    calls = {"source": 0, "environment": 0}
+    events, interruptions = [], []
+    args.on_progress = events.append
+    original = Checkpoints.source
+
+    def reached(kind):
+        calls[kind] += 1
+        if kind == probe and events and events[-1]["phase"] == "finalizing":
+            # Intermediate checkpoint probes are also real verification. Target
+            # finalization explicitly, while the runner owns signal handlers.
+            interruptions.append(kind)
+            os.kill(os.getpid(), interruption)
+
+    def source(self, *values, **kwargs):
+        reached("source")
+        return original(self, *values, **kwargs)
+
+    def environment(*_args, **_kwargs):
+        reached("environment")
+        return "fixture-environment"
+
+    monkeypatch.setattr(Checkpoints, "source", source)
+    monkeypatch.setattr(runner, "environment_fingerprint", environment)
+    result = runner.run_checks(args, [fixtures.stage(repo)])
+    assert interruptions == [probe]
+    assert calls[probe] >= 2
+    assert result["stages"][0]["status"] == "passed"
+    assert result["status"] == "interrupted"
+    assert result["_exit_code"] != 0
+    receipt = runner.read_receipt(args.workspace_root, args.state_dir, result["run_id"])
+    assert receipt["status"] == "interrupted"
+
+
+@pytest.mark.parametrize("interruption", [signal.SIGINT, signal.SIGTERM])
+@pytest.mark.parametrize("probe", ["source", "environment"])
+def test_preparation_interrupt_stops_at_probe_boundary_without_running_checks(
+    example, monkeypatch, interruption, probe
+):
+    args, repo = example
+    calls = []
+    original = Checkpoints.source
+
+    def reached(kind):
+        calls.append(kind)
+        if kind == probe:
+            os.kill(os.getpid(), interruption)
+
+    def source(self, *values, **kwargs):
+        reached("source")
+        return original(self, *values, **kwargs)
+
+    def environment(*_args, **_kwargs):
+        reached("environment")
+        return "fixture-environment"
+
+    def must_not_execute(*args, **kwargs):
+        pytest.fail("A cancelled preparation must not start a check")
+
+    monkeypatch.setattr(Checkpoints, "source", source)
+    monkeypatch.setattr(runner, "environment_fingerprint", environment)
+    monkeypatch.setattr(runner, "execute_stage", must_not_execute)
+    result = runner.run_checks(args, [fixtures.stage(repo)])
+    assert calls == (["source"] if probe == "source" else ["source", "environment"])
+    assert result["status"] == "interrupted"
+    assert result["snapshot_verified"] is False
+    assert result["_exit_code"] != 0
+    receipt = runner.read_receipt(args.workspace_root, args.state_dir, result["run_id"])
+    assert receipt["status"] == "interrupted"