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/src/nisse_dev/state.py

@@ -28,6 +28,7 @@ from nisse_dev.canonical import (
     to_payload,
 )
 from nisse_dev.oplog import OpLog
+from nisse_dev.views import project
 
 CURRENT_SCHEMA_VERSION = 4
 
@@ -619,8 +620,14 @@ class Transcript:
         return self._store._append(event, self.work_item, self.actor)
 
     def read(self, after: int = 0) -> list[StoredEvent]:
+        """The log as recorded: every role's events, for the record."""
         return self._store._read(self.work_item, after)
 
+    def view(self, after: int = 0) -> list[StoredEvent]:
+        """The log as this actor is shown it: what a model's context is
+        built from (L6). See ``views``."""
+        return project(self.read(after), self.actor)
+
     def as_actor(self, actor: str) -> "Transcript":
         """The same work item, written by another role: e.g. the executor
         handing a sub-task to the helper."""