fix(content): keep coordination notes off dev_notes / quick_context

Two agent-authored fields were leaking non-developer content into the
human note columns the panel renders:

- apply_escalation appended '[ESCALATED] From X to Y\nReason: ...' to
  dev_notes (the developer's space). On a re-escalation loop a stuck cell
  PM grew one task's dev_notes to ~8KB across 5 escalations. It now writes
  a structured orchestration_markers['escalation'] record; the target
  still learns the reason from the escalate notification.
- approve_and_start string-packed 'approve_and_start_notes:<text>' into
  quick_context (raw key:value soup). It now writes
  orchestration_markers['approve_and_start_notes'], leaving quick_context
  for the human ResumptionNote only.

Adds typed marker accessors (get/set_escalation, get/set_approve_and_start_notes)
and refactors _record_pr_review under the complexity bound by extracting
_compose_review_body. Documents update_task_with_message as the legacy
A2A-protocol log (dev_notes is intentional there, not pollution).

roboco/services/a2a.py

@@ -539,7 +539,14 @@ class A2AService:
 
     @staticmethod
     def update_task_with_message(task: TaskTable, message: A2AMessage) -> None:
-        """Update an existing task's dev_notes with new message content."""
+        """Append A2A-protocol message text to the task's A2A log (dev_notes).
+
+        NOTE: this is the *legacy A2A-protocol* message store — A2A-protocol
+        tasks carry their request/response thread in ``dev_notes`` (keyed by the
+        ``"A2A Request"`` marker that ``_notify_original_requester`` checks).
+        It is NOT the gateway agent flow (those use the A2AConversation tables),
+        so it does not pollute normal delivery tasks' developer notes.
+        """
         text_parts = [p for p in message.parts if p.type == "text"]
         if not text_parts:
             return