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

docs/Architecture.md

@@ -386,8 +386,13 @@ the caller treats it as a failure (L9).
   happened from these, not by inferring it.
 - **Each role gets its own view:**
   - the driver sees the conversation, the facts, and helpers' reports;
-  - a helper (delegation, `ask_expert`) sees its brief and its own work;
-  - no role sees another role's raw turns presented as its own.
+  - a delegated helper sees its brief, the approved plan, the facts, its own work,
+    and the driver's work in the same milestone as compact narration (each step
+    and how it went);
+  - `ask_expert` is stateless: the expert sees only the question;
+  - no role sees another role's raw turns presented as its own. Whatever is not
+    the viewer's own reaches it as input labelled with its origin
+    (`[orchestrator]`, `[operator, Matrix]`, `[helper report]`).
 
 **3. Scope memory** — outlives work items.
 - **For a repo:** the project's own documents (`ARCHITECTURE.md`, build plans,