feat(zcode-grokbot-dispatch): add Grok Bot Dispatch for ZCode

[semantic-craft]

Plugin type (required) / 插件类型（必填）

• UI Plugin / 是 UI 插件
• Standard plugin / 普通插件（非 UI） — does not provide MCP Apps interactive pages / 不提供 MCP Apps 交互页面
• Not applicable / 不适用

Affected plugin name(s) / 涉及的插件名称：zcode-grokbot-dispatch (Standard plugin)

What / 改动内容

Adds new external plugin Grok Bot Dispatch for ZCode (id zcode-grokbot-dispatch, directory external_plugins/zcode-grokbot-dispatch/) and its marketplace.json entry (v0.3.0, category productivity).
Bidirectional task dispatch between ZCode desktop and Grok Bot / DSH (DeepSeek Harness): [Project: X] routing, persistent session↔job mapping, automatic result reporting back to your Grok Bot peer via the Stop hook (direct HTTP by default, Yobiru optional). Only the plugin client is included — no receiver/server code and no built-in endpoints. Source: https://github.com/semantic-craft/zcode-dispatch (MIT).

新增外部插件 zcode-grokbot-dispatch（Grok Bot Dispatch for ZCode）：ZCode 与 Grok Bot / DSH 双向派活，结果自动回报给 Grok Bot 对端。仅包含插件客户端，不含接收端，不内置任何 endpoint。

Install / repro steps (from README)

1. ZCode → Settings → Plugins → zcode-plugins-official → install zcode-grokbot-dispatch.
2. Requires Node.js ≥ 22.5 on PATH. /dispatch-dsh also requires the dsh CLI (override with DSH_BIN).
3. Configure peers in ~/.config/zcode-dispatch/config.json or env vars (env wins), e.g.
   { "transport": "direct", "peers": { "dsh": { "url": "http://<peer-host>:<port>", "keyFile": "~/.config/zcode-dispatch/dsh.key" } } }
   Env: ZCODE_DISPATCH_CONFIG, ZCODE_DISPATCH_TRANSPORT (direct|yobiru), ZCODE_DISPATCH_GROK_PEER, ZCODE_DISPATCH_PROJECTS_ROOT, ZCODE_DISPATCH_DISCOVERY=0, DSH_BIN, DSH_PROFILE.
4. Run /dispatch-grok <project> <task>, /dispatch-dsh <project> <task> or /dispatch-status <id>; nothing is sent until a peer is configured.

Side effects (network only to the user-configured peer; commands dsh / yobiru / tailscale status; state under ~/.local/state/zcode-dispatch/; hooks on UserPromptSubmit/Stop) are documented in README.md / README_CN.md. No telemetry.

Note: runtime config/state paths keep the zcode-dispatch name; only the marketplace id/display name carries Grok Bot. 运行时路径沿用 zcode-dispatch，仅插件 id/展示名包含 Grok Bot。

Self-check / 自查清单

• Plugin name zcode-grokbot-dispatch is unique kebab-case; directory external_plugins/zcode-grokbot-dispatch/
• category set (productivity)
• Plugin type and names declared above
• version 0.3.0 in both plugin.json and marketplace.json (new plugin)
• README.md and README_CN.md both present and equivalent
• description_i18n has en and zh-CN
• No secrets, machine-specific paths, or private dependencies (Node built-ins only)
• Network/command dependencies documented
• python3 scripts/validate.py passes (OK: 46 plugin(s) validated). scripts/build_dist.py fails locally on the unrelated existing blender plugin (incomplete build; run pnpm build first), not on this plugin.

[panda920]

✅ Internal validation passed. A ZCode maintainer will review the change next; after acceptance, release checks run separately and this PR is closed automatically.