Workplan terminology: templates, updater guard, add_progress_event alias

- project_rules templates: rename workstream->workplan in prose; registration
  guidance is now file-first + fix-consistency C-06 (manual create_workplan/
  create_workstream calls create duplicates); progress examples use
  workplan_id; legacy field names (state_hub_workstream_id) annotated
- update_agent_instruction_files: never overwrite filled-in
  stack-and-commands/repo-boundary/architecture rules (TODO-marker guard)
- mcp_server: add_progress_event accepts workplan_id (preferred) with
  workstream_id kept as legacy alias, mirroring create_task

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

mcp_server/server.py

@@ -989,6 +989,7 @@ def add_progress_event(
     summary: str,
     event_type: str = "note",
     topic_id: str | None = None,
+    workplan_id: str | None = None,
     workstream_id: str | None = None,
     task_id: str | None = None,
     detail: dict | str | None = None,
@@ -999,7 +1000,8 @@ def add_progress_event(
         summary: human-readable summary of what happened
         event_type: free-form label, e.g. note | milestone | blocker | insight
         topic_id: optional topic UUID
-        workstream_id: optional workstream UUID
+        workplan_id: optional workplan UUID (preferred)
+        workstream_id: legacy alias for workplan_id
         task_id: optional task UUID
         detail: optional structured data (JSONB); accepts a dict or a JSON string
     """
@@ -1010,7 +1012,7 @@ def add_progress_event(
             detail = {"raw": detail}
     event = _post("/progress", {
         "topic_id": topic_id,
-        "workstream_id": workstream_id,
+        "workplan_id": workplan_id or workstream_id,
         "task_id": task_id,
         "event_type": event_type,
         "summary": summary,