Give each role its own view of the transcript (M1.2)

A model no longer reads another role's turns as its own (#78). The log
stays one record per work item; what a role is shown is projected from
it by Transcript.view() (views.py), which the planner, executor and
helper now build their context from:

- own events unchanged;
- operator messages labelled with their channel, e.g.
  [operator, Matrix] or [operator, comment on PR #165];
- orchestrator facts (a new `fact` event) as [orchestrator] statements;
- the executor sees a helper's handback as [helper report], not its turns;
- a helper sees the approved plan and the executor's milestone work as
  one-line narration;
- the planner sees no other role's work at all.

The orchestrator now writes facts at the points the models must know
about: work item opened, plan approved or rejected, milestone started,
finished or stopped, published (with PR number and URL) or not, review
comment answered, next milestone, task completed or abandoned.

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

nisse-dev/tests/test_planner.py

@@ -170,8 +170,8 @@ def test_planner_sees_prior_transcript(store: StateStore) -> None:
     )
     client = ScriptedClient([[plan_call("plan")]])
     LLMPlanningAgent(client, ROLES).plan(log(store), "arch", "demo")
-    seen = [e.event for e in client.calls[0]["events"]]
-    assert UserMessage(text="use demo", source="transport:@don") in seen
+    seen = [getattr(e.event, "text", None) for e in client.calls[0]["events"]]
+    assert "[operator, Matrix] use demo" in seen
 
 
 # --- orchestrator integration (still no network) -------------------------
@@ -202,6 +202,7 @@ def test_use_project_produces_llm_plan_and_transcript(tmp_path: Path) -> None:
     kinds = [type(e).__name__ for e in events]
     assert kinds == [
         "UserMessage",
+        "Fact",
         "ToolCall",
         "ToolResult",
         "PlanSubmitted",