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>

scripts/update_agent_instruction_files.py

@@ -27,6 +27,10 @@ def fetch(path: str):
 
 EXTENSION_MARKER = "<!-- REPO-AGENTS-EXTENSIONS -->"
 
+# Rule files that repos fill in with local content; only (re)write them while
+# they still contain the template's TODO markers.
+PRESERVE_IF_CUSTOMIZED = {"stack-and-commands", "repo-boundary", "architecture"}
+
 
 def render(template: str, values: dict[str, str]) -> str:
     for key, value in values.items():
@@ -188,7 +192,13 @@ def update_repo(
     rules_dir = path / ".claude" / "rules"
     rules_dir.mkdir(parents=True, exist_ok=True)
     for name, template in rule_templates.items():
-        (rules_dir / f"{name}.md").write_text(render(template, values), encoding="utf-8")
+        target = rules_dir / f"{name}.md"
+        if name in PRESERVE_IF_CUSTOMIZED and target.exists():
+            # These files start as TODO templates and get filled per repo;
+            # never overwrite a filled-in version with the blank template.
+            if "TODO" not in target.read_text(encoding="utf-8"):
+                continue
+        target.write_text(render(template, values), encoding="utf-8")
 
     return f"{repo_slug}\t{path}\t{prefix}"