refactor: migrate delegate_task to task tool with metadata fixes

- Rename delegate_task tool to task across codebase (100 files)
- Update model references: claude-opus-4-6 → 4-5, gpt-5.3-codex → 5.2-codex
- Add tool-metadata-store to restore metadata overwritten by fromPlugin()
- Add session ID polling for BackgroundManager task sessions
- Await async ctx.metadata() calls in tool executors
- Add ses_ prefix guard to getMessageDir for performance
- Harden BackgroundManager with idle deferral and error handling
- Fix duplicate task key in sisyphus-junior test object literals
- Fix unawaited showOutputToUser in ast_grep_replace
- Fix background=true → run_in_background=true in ultrawork prompt
- Fix duplicate task/task references in docs and comments

src/shared/permission-compat.ts

@@ -73,5 +73,14 @@ export function migrateAgentConfig(
     delete result.tools
   }
 
+  if (result.permission && typeof result.permission === "object") {
+    const perm = { ...(result.permission as Record<string, PermissionValue>) }
+    if ("delegate_task" in perm && !("task" in perm)) {
+      perm["task"] = perm["delegate_task"]
+      delete perm["delegate_task"]
+      result.permission = perm
+    }
+  }
+
   return result
 }