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.

nix/checks.nix

@@ -154,8 +154,7 @@ json.dump(sorted(leaf_paths(DEFAULT_CONFIG)), sys.stdout, indent=2)
           test -f ${hermes-agent}/ui-tui/dist/entry.js || (echo "FAIL: compiled entry.js missing"; exit 1)
           echo "PASS: compiled entry.js present"
 
-          test -d ${hermes-agent}/ui-tui/node_modules || (echo "FAIL: node_modules missing"; exit 1)
-          echo "PASS: node_modules present"
+          # self-contained bundle; no runtime node_modules expected
 
           grep -q "HERMES_TUI_DIR" ${hermes-agent}/bin/hermes || \
             (echo "FAIL: HERMES_TUI_DIR not in wrapper"; exit 1)