feat: add OpenClaw plugin manifest and entry point

- Add openclaw.plugin.json with proper configSchema
- Add index.js as plugin entry point
- Fix plugin id to 'padded-cell' to match manifest

index.js

@@ -0,0 +1,21 @@
+// PaddedCell Plugin Entry Point
+export const id = 'padded-cell';
+export const name = 'PaddedCell';
+export const version = '0.1.0';
+
+// Export tools (will be loaded by OpenClaw)
+export { pcexec } from './pcexec/dist/index.js';
+export { 
+  safeRestart, 
+  createSafeRestartTool, 
+  StatusManager, 
+  createApiServer,
+  startApiServer 
+} from './safe-restart/dist/index.js';
+
+// Default export
+export default {
+  id,
+  name,
+  version,
+};