feat: plugin-registry 标准发布面（dsh.plugin.json + 双 client bundle + registry 打包），v0.1.2

- dsh.plugin.json 原生清单：id dsh-external/dsh-better-sidebar，version 0.1.2，
  main = lib/index.js，client.main = lib/client-registry.js，contributes 空声明
- tsdown client 构建参数化：lib/client.js（官方通道，id = 包名）+ lib/client-registry.js
  （registry 通道，id = 清单 id），同源不漂移
- scripts/package-registry.mjs 组装 registry/ 安装根（gitignore，不入库）
- tests/manifest-consistency.spec.ts：id 两段校验 / version 同步 / 入口存在 /
  双 bundle id 不互换 / contributes 空
- README：新增「通过 plugin-registry 安装（标准）」章节 + 保留官方 profile 安装
  方案 + 通道互斥说明；架构表补 manifest 与双 client 行

scripts/package-registry.mjs

@@ -0,0 +1,49 @@
+#!/usr/bin/env node
+/**
+ * Assemble the plugin-registry installable root (`registry/`) from the built
+ * `lib/` output. Run after `pnpm build`:
+ *
+ *   pnpm build
+ *   node scripts/package-registry.mjs
+ *   dsh registry install ./registry
+ *   dsh registry enable dsh-external/dsh-better-sidebar
+ *
+ * The registry install copies the whole source directory (`cp -r`), so
+ * installing the repo root would drag in `node_modules/` (machine-local
+ * `link:` devDependency symlinks, node-pty binaries) and `.git/`. This
+ * staging directory carries exactly the files the manifest references plus
+ * the docs — same layout as the dsh-subagent-tree `registry/` pattern. It is
+ * gitignored and rebuilt from scratch on every run.
+ */
+import { cpSync, existsSync, mkdirSync, rmSync } from 'node:fs'
+import { dirname, join, resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const root = resolve(fileURLToPath(import.meta.url), '..', '..')
+const out = join(root, 'registry')
+
+/** Files copied into registry/, preserving relative paths (lib/ stays lib/). */
+const files = [
+  'dsh.plugin.json',
+  'lib/index.js',
+  'lib/invariant.js',
+  'lib/client-registry.js',
+  'lib/client-registry.js.map',
+  'README.md',
+  'LICENSE',
+]
+
+rmSync(out, { recursive: true, force: true })
+mkdirSync(out, { recursive: true })
+for (const file of files) {
+  const source = join(root, file)
+  if (!existsSync(source)) {
+    console.error(`missing ${file} — run \`pnpm build\` first`)
+    process.exit(1)
+  }
+  const target = join(out, file)
+  mkdirSync(dirname(target), { recursive: true })
+  cpSync(source, target)
+}
+console.log(`registry/ assembled (${files.length} files)`)
+console.log('next: dsh registry install ./registry && dsh registry enable dsh-external/dsh-better-sidebar')