Retire the readline front door and the repl-agent example

Delete packages/ui/stdio and examples/repl-agent; rename stdio-demo to
@deepseek-ai/dsh-tui-demo (TUI-only, refuses pipes before Loader boot).
tui-agent owns the coding composition inline; echo-agent and the CI demo
smoke move to the one-shot cli-demo bin, which gains -p/--prompt. The
UI-independent with-key e2es move verbatim to tui-agent. SDK wizard's
'stdio' interface becomes 'tui'. PTY testing stays confined to TUI
surfaces; all other subprocess tests ride pipes.

See .agents/notes/implemented/simplification/2026-07-20-retire-readline-front-door.md

package.json

@@ -10,6 +10,7 @@
   "workspaces": [
     "vendor/*",
     "packages/*/*",
+    "apps/*",
     "website"
   ],
   "scripts": {
@@ -81,7 +82,7 @@
     "doc-sync": "tsx scripts/run-gates.ts doc-sync",
     "hygiene": "pnpm run knip && pnpm run publint && pnpm run constraints && pnpm run verify-package-invariants && pnpm run verify-built-package-invariants && pnpm run verify-cordis-config && pnpm run verify-node-next-types && pnpm run verify-runtime-closure",
     "demo:headless": "node --expose-internals --import tsx packages/examples/cli-demo/src/bin.ts --config examples/headless-agent/cordis.yml",
-    "demo:tui": "node --expose-internals --import tsx packages/examples/tui-demo/src/bin.ts examples/tui-agent/cordis.yml",
+    "demo:tui": "node --expose-internals --import tsx apps/cli/src/bin.ts",
     "demo:code-mode": "node scripts/demo-code-mode.mjs",
     "demo:cordis": "node --expose-internals --import tsx packages/examples/tui-demo/src/bin.ts examples/cordis-agent/cordis.yml",
     "demo:acp": "node --import tsx packages/examples/acp-demo/src/bin.ts --config examples/acp-agent/cordis.yml",