refactor(tui): bundle with esbuild, drop runtime node_modules

Replace the tsc + babel pipeline with a single esbuild invocation that
produces a self-contained dist/entry.js. The nix TUI derivation no
longer copies node_modules — only dist/ + package.json ship, shrinking
the output from hundreds of MB to ~2.9 MB.

- ui-tui/scripts/build.mjs: new esbuild bundler. Aliases @hermes/ink
  to source (esbuild's __esm helper doesn't await nested async init,
  which breaks lazy-assigned exports like 'render' when re-exporting
  through a prebuilt submodule). Stubs react-devtools-core (dev-only).
  Injects a createRequire shim for transitive CJS deps. Strips the
  shebang from src/entry.tsx because Nix patchShebangs mangles
  '/usr/bin/env -S node --max-old-space-size=8192 --expose-gc' — it
  drops the 'node' token. The Python launcher always invokes node
  explicitly, so the shebang is redundant.
- nix/tui.nix: installPhase no longer copies node_modules or the
  @hermes/ink packages dir.
- nix/checks.nix: drop the 'node_modules present' assertion.
- hermes_cli/main.py: _tui_need_npm_install short-circuits when
  dist/entry.js exists and no package-lock.json is present. That is
  the prebuilt-bundle layout (nix / packaged release) and there is
  nothing to install. Without this, the launcher tried to npm install
  in a non-existent site-packages/ui-tui path.

ui-tui/package.json

@@ -6,8 +6,7 @@
   "scripts": {
     "dev": "npm run build --prefix packages/hermes-ink && tsx --watch src/entry.tsx",
     "start": "tsx src/entry.tsx",
-    "build": "npm run build --prefix packages/hermes-ink && tsc -p tsconfig.build.json && npm run build:compile && chmod +x dist/entry.js",
-    "build:compile": "babel dist --out-dir dist --config-file ./babel.compiler.config.cjs --extensions .js --keep-file-extension",
+    "build": "node scripts/build.mjs",
     "type-check": "tsc --noEmit -p tsconfig.json",
     "lint": "eslint src/ packages/",
     "lint:fix": "eslint src/ packages/ --fix",
@@ -34,6 +33,7 @@
     "@typescript-eslint/eslint-plugin": "^8",
     "@typescript-eslint/parser": "^8",
     "babel-plugin-react-compiler": "^1.0.0",
+    "esbuild": "~0.27.0",
     "eslint": "^9",
     "eslint-plugin-perfectionist": "^5",
     "eslint-plugin-react": "^7",