fix(nix): package local speech worker (#1587)

* fix(nix): package local speech worker

* fix(nix): reuse sherpa package helper

* fix(nix): patch sherpa-onnx prebuilt binaries for NixOS libstdc++

The prebuilt sherpa-onnx-linux-x64 .so files link against libstdc++.so.6
which is not on the NixOS library path. Add autoPatchelfHook to fix ELF
RPATHs and stdenv.cc.cc.lib to provide the C++ runtime, resolving the
"Failed to load model because protobuf parsing failed" SIGABRT at
speech worker startup.

nix/package.nix

@@ -5,6 +5,7 @@
   nodejs_22,
   python3,
   makeWrapper,
+  autoPatchelfHook,
   # node-pty needs libuv headers on Linux
   libuv,
   # Exposed so downstream flakes that follow a different nixpkgs revision
@@ -59,10 +60,13 @@ buildNpmPackage rec {
   nativeBuildInputs = [
     python3 # for node-gyp (node-pty compilation)
     makeWrapper
+  ] ++ lib.optionals stdenv.hostPlatform.isLinux [
+    autoPatchelfHook
   ];
 
   buildInputs = lib.optionals stdenv.hostPlatform.isLinux [
     libuv
+    stdenv.cc.cc.lib # libstdc++ for sherpa-onnx prebuilt binaries
   ];
 
   # Don't use the default npm build hook — we need a custom build sequence
@@ -71,10 +75,9 @@ buildNpmPackage rec {
   buildPhase = ''
     runHook preBuild
 
-    # Rebuild only node-pty (native addon for terminal emulation).
-    # Speech-related native modules (sherpa-onnx, onnxruntime-node) are
-    # intentionally left unbuilt — they're lazily loaded and gracefully
-    # degrade when unavailable.
+    # Rebuild only node-pty (native addon for terminal emulation). The sherpa
+    # speech runtime ships prebuilt platform packages and is copied into the
+    # daemon closure by scripts/trace-daemon.mjs.
     npm rebuild node-pty
 
     # Build all server packages in dependency order (defined in package.json)
@@ -89,7 +92,7 @@ buildNpmPackage rec {
 
     # Compute the daemon's runtime closure by static module-graph tracing
     # (@vercel/nft from supervisor-entrypoint.js, cli/dist/index.js, and the
-    # forked terminal-worker-process.js) plus an explicit list of non-JS
+    # forked terminal/speech worker processes) plus an explicit list of non-JS
     # assets read at runtime. The trace script is the single source of
     # truth for what the daemon needs at $out — auditable in plain JS, no
     # npm hoisting / .bin / workspace-symlink footguns.