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.

tsconfig.json

@@ -72,6 +72,7 @@
     { "path": "./packages/ui/app-boot" },
     { "path": "./packages/ui/jsonrpc" },
     { "path": "./packages/examples/jsonrpc-demo" },
+    { "path": "./packages/ui/tui" },
     { "path": "./packages/ui/stdio" },
     { "path": "./packages/examples/stdio-demo" },
     { "path": "./packages/support/llm-replay" },