refactor(util): extract the shared no-shell native-command runner to dsh-native-command

master's toolcall-open extracted runNativeCommand inside apiproxy for the
openPath opener while the picker seam had moved the native chooser (its other
consumer) into directory-picker-native; after the merge the two packages each
carried a verbatim copy. The runner now lives in packages/util/native-command
(zero-dependency library, per the util-group contract) and both native
integrations depend on it.

tsconfig.host.json

@@ -46,6 +46,7 @@
     { "path": "./vendor/hmr" },
     { "path": "./vendor/logger-console" },
     { "path": "./packages/util/brand" },
+    { "path": "./packages/util/native-command" },
     { "path": "./packages/util/paths" },
     { "path": "./packages/util/timeout" },
     { "path": "./packages/util/retention" },