Add control loop, gating primitives, and transport interface (A4/B1)

Step-2 PR A: the approval loop end to end with a stub agent, no LLM
and no network.

- transport.py: Transport interface per A1 (send_message,
  send_approval_request, ask_question, on_message) with an
  InMemoryTransport; no platform SDK outside an implementation
- gates.py: PlanRevision with monotonic rev-N tags; Gate.evaluate
  enforces revision binding (stale tags refused with a notice),
  operator allowlisting, and approve-word-only semantics; any other
  reply is rejection feedback. Channel seam ready for Gitea/Vikunja
  approval sources
- control.py: B1 state machine subset with structural gating — the
  agent's only actions are SubmitPlan (ends its turn) and AskHuman;
  no proceed tool exists. Gate state, revision counters, task_id,
  and pending questions checkpoint through StateStore, and boot
  resumes an open gate or gates to AWAIT_INPUT, never blind-resumes
- gate.open/approve/reject A9 events complete the log taxonomy
- CLAUDE.md: record the plan-first working convention
- Tests: 15 unit (gates + orchestrator flows), 2 integration
  (mid-gate restart with revisions intact; unresolved intents gate
  the whole boot)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/integration/test_gate_restart.py

@@ -0,0 +1,65 @@
+"""Integration: a restart mid-gate resumes the open gate with its revision
+history intact; unresolved intents gate the whole boot to AWAIT_INPUT
+(spec A2/A3/A4 together)."""
+
+import io
+from pathlib import Path
+
+import pytest
+
+from nisse_dev.control import (
+    AWAIT_ARCH_SIGNOFF,
+    AWAIT_INPUT,
+    AWAIT_MILESTONE_SIGNOFF,
+    Orchestrator,
+    StubAgent,
+)
+from nisse_dev.oplog import OpLog
+from nisse_dev.state import StateStore
+from nisse_dev.transport import InMemoryTransport
+
+pytestmark = pytest.mark.integration
+
+
+def boot(db: Path) -> tuple[Orchestrator, StateStore, InMemoryTransport]:
+    store = StateStore(db, oplog=OpLog("nisse-dev", io.StringIO()))
+    transport = InMemoryTransport()
+    orch = Orchestrator(store, transport, StubAgent(), operators={"don"})
+    orch.start()
+    return orch, store, transport
+
+
+def test_restart_mid_gate_resumes_with_revisions_intact(tmp_path: Path) -> None:
+    db = tmp_path / "state.db"
+    _, store, transport = boot(db)
+    transport.receive("don", "use demo")
+    transport.receive("don", "needs work")  # arch gate now at rev-2
+    task_id = store.oplog.task_id
+    store.close()
+
+    _, store2, transport2 = boot(db)
+    state = store2.get_state()
+    assert state is not None
+    assert state.state == AWAIT_ARCH_SIGNOFF
+    assert store2.oplog.task_id == task_id  # correlation survives restart
+    notices = [m.text for m in transport2.outbound]
+    assert any("rev-2" in n and "still open" in n for n in notices)
+
+    transport2.receive("don", "approve rev-1")  # stale across the restart too
+    assert store2.get_state().state == AWAIT_ARCH_SIGNOFF
+    transport2.receive("don", "approve rev-2")
+    assert store2.get_state().state == AWAIT_MILESTONE_SIGNOFF
+
+
+def test_restart_with_unresolved_intent_gates_boot(tmp_path: Path) -> None:
+    db = tmp_path / "state.db"
+    _, store, transport = boot(db)
+    transport.receive("don", "use demo")
+    store.begin_intent("push_branch", {"branch": "m1"}, cause="test")
+    store.close()
+
+    _, store2, transport2 = boot(db)
+    assert store2.get_state().state == AWAIT_INPUT
+    question = transport2.outbound[-1]
+    assert question.kind == "question"
+    assert "unresolved work" in question.text