Put work items in the state store, and bind the log to them (M1.1)

Development Plan M1.1, as discussed.

- Schema v4: a work_items table (id, scope, title, status, outcome,
  position, data) and an agent row whose active_item points at one
  (NULL: idle). Canonical events and intents carry their work item, and
  events their actor. Older stores are refused with a clear message:
  there was no production data, so no migration (the mechanism stays).
- The log is reached through a Transcript bound to one work item and
  one actor: store.transcript(item, actor) reads only that item and
  writes with both. The planner, executor, delegation and expert desk
  get one per call from the orchestrator instead of holding the store,
  so a component can neither read another task's events (the planner
  read every earlier task's, #78) nor write without attribution.
  store.all_events() is kept for readers that span items (evaluation
  capture, dumps). Intents are begun through the transcript or with
  work_item=, so each belongs to its item.
- The orchestrator opens a work item on 'use', closes it with its
  outcome (completed or abandoned), and carries what the operator said
  while idle into the new item as copies with their origin, so a task
  sent before 'use' is still planned from (D1). control.py keeps its
  state machine through get_state()/transition(), now over the active
  work item, until M2.6 retires it.
- nisse_dev.dump shows work items and each event's item and actor.

Tests: test_work_items.py (scoping, attribution, intent ownership,
restart, outcomes, carried messages, a second task never seeing the
first); the suites updated for the per-call transcript.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

tests/integration/test_crash_durability.py

@@ -21,7 +21,7 @@ from nisse_dev.state import StateStore
 store = StateStore(sys.argv[1])
 store.transition("EXECUTING", cause="test", project="demo", data={"milestone": 2})
 store.begin_intent("push_branch", {"branch": "milestone-2"}, cause="test")
-store.append_event(UserMessage(text="start milestone 2", source="m:1"))
+store.transcript("t", "operator").append(UserMessage(text="start milestone 2", source="m:1"))
 os._exit(1)  # die without closing anything, as a power cut would
 """
 
@@ -48,5 +48,5 @@ def test_state_survives_process_death(tmp_path: Path) -> None:
         [pending] = store.pending_intents()
         assert pending.payload == {"branch": "milestone-2"}
 
-        [stored] = store.read_events()
+        [stored] = store.all_events()
         assert stored.event.text == "start milestone 2"