feat(ui): add dedicated TUI package

Move the interactive pi-tui front door into @deepseek-ai/dsh-tui while keeping @deepseek-ai/dsh-stdio line-oriented for pipes. Select the terminal package in the demo app, preserve logger ownership, and cover the production Loader composition with a PTY smoke test.

packages/ui/tui/tests/plugin-shape.spec.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from 'vitest'
+import Loader from '@cordisjs/plugin-loader'
+import * as tui from '../src/index.ts'
+
+/** Real Loader export-path guard for the namespace TUI plugin. */
+describe('dsh-tui plugin export shape', () => {
+  it('preserves name, inject, Config, and apply through Loader unwrapping', () => {
+    expect('default' in tui).toBe(false)
+    expect(typeof tui.apply).toBe('function')
+
+    const loader = Object.create(Loader.prototype) as Loader
+    const unwrapped = loader.unwrapExports(tui) as Record<string, unknown>
+    expect(unwrapped).toBe(tui)
+    expect(unwrapped.name).toBe('ui-tui')
+    expect(unwrapped.inject).toEqual(['agents', 'userInteraction', 'tools'])
+    expect(unwrapped.Config).toBeDefined()
+    expect(typeof unwrapped.apply).toBe('function')
+  })
+})