chore: retire TODO.md in favour of workplans

Drop the repo-level Todofile; active work lives in workplans/ and State
Hub per ADR-001. Schedule prepare now surfaces workplans/ instead of
TODO.md. Gitignore .kaizen/agents/ and .kaizen/metrics/ runtime state.

src/kaizen_agentic/cli.py

@@ -1704,10 +1704,12 @@ def _build_prepare_bundle(agent_name: str, project_root: Path) -> dict:
         metrics_summary = metrics_store.write_summary()
 
     pointers = {}
-    for label, filename in (("scope", "SCOPE.md"), ("todo", "TODO.md")):
-        candidate = project_root / filename
-        if candidate.exists():
-            pointers[label] = str(candidate)
+    scope_path = project_root / "SCOPE.md"
+    if scope_path.exists():
+        pointers["scope"] = str(scope_path)
+    workplans_path = project_root / "workplans"
+    if workplans_path.is_dir():
+        pointers["workplans"] = str(workplans_path)
 
     return {
         "agent": agent_name,
@@ -1762,7 +1764,7 @@ def _render_prepare_markdown(bundle: dict) -> str:
         for label, path in pointers.items():
             lines.append(f"- {label}: {path}")
     else:
-        lines.append("- (no SCOPE.md / TODO.md found)")
+        lines.append("- (no SCOPE.md / workplans/ found)")
     lines.append("")
 
     lines.append("## Session Close")