Use goose port (#7089)

Co-authored-by: Douwe Osinga <douwe@squareup.com>

Justfile

@@ -144,7 +144,6 @@ debug-ui *alpha:
     @echo "🚀 Starting goose frontend in external backend mode{{ if alpha == "alpha" { " with alpha features enabled" } else { "" } }}"
     cd ui/desktop && \
     export GOOSE_EXTERNAL_BACKEND=true && \
-    export GOOSE_EXTERNAL_PORT=3000 && \
     {{ if alpha == "alpha" { "export ALPHA=true &&" } else { "" } }} \
     npm install && \
     npm run {{ if alpha == "alpha" { "start-alpha-gui" } else { "start-gui" } }}

ui/desktop/src/goosed.ts

@@ -105,7 +105,8 @@ export const startGoosed = async (options: StartGoosedOptions): Promise<GoosedRe
   }
 
   if (process.env.GOOSE_EXTERNAL_BACKEND) {
-    return connectToExternalBackend(dir, 'http://127.0.0.1:3000');
+    const port = process.env.GOOSE_PORT || '3000';
+    return connectToExternalBackend(dir, `http://127.0.0.1:${port}`);
   }
 
   let goosedPath = getGoosedBinaryPath(app);