fix: replace /plan with instruction-based planning prefix (v3.3.1)

Closes #60. The /plan slash command is only available in Claude Code's
interactive TTY mode, not in --stream-json or custom engines.

Tested across Claude Code, Codex, and Gemini CLI.

Author: Enderfga

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.3.1] - 2026-05-07
+
+### Fixed
+
+- **#60 — `/plan` isn't available in this environment.** The `plan: true` option in `sendMessage` previously prepended `/plan` to the message, which is a Claude Code interactive-only slash command not available in `--stream-json` mode or any other engine. Replaced with a universally compatible instruction-based planning prefix (`[Planning Mode] ...`) in both `persistent-session.ts` and `persistent-custom-session.ts`. Tested across Claude Code, Codex, and Gemini.
+
 ## [3.3.0] - 2026-05-06
 
 ### Added — `engine: 'opencode'` for [sst/opencode](https://github.com/sst/opencode)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@enderfga/claw-orchestrator",
-  "version": "3.3.0",
+  "version": "3.3.1",
   "description": "Claw Orchestrator — run Claude Code, Codex, Gemini, Cursor Agent, OpenCode and custom coding CLIs as one unified runtime for claw-style agent systems. Runs standalone, with first-class OpenClaw plugin support. Persistent sessions, multi-agent council, tool orchestration.",
   "type": "module",
   "main": "./dist/src/index.js",