refactor: simplify TextDecoder allocation, O(N) string concat, consolidate imports

- Hoist TextDecoder to module-level constant in client.ts and stream.ts
- Replace O(N^2) string concatenation in execCollect with array + join
- Consolidate three imports from generated/openshell.js into one
- Reuse module-level EMPTY_BYTES constant for stdin default
- Remove vitest globals: true (test files import explicitly)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rrodrigu3z

src/client.ts

@@ -5,11 +5,15 @@ import { createChannel, createClient, type Channel } from "nice-grpc";
 import { credentials as grpcCredentials } from "@grpc/grpc-js";
 import {
   OpenShellDefinition,
+  serviceStatusToJSON,
   type OpenShellClient as GeneratedClient,
+  type ExecSandboxEvent,
+  type CreateSandboxRequest,
 } from "./generated/openshell.js";
-import type { ExecSandboxEvent, CreateSandboxRequest } from "./generated/openshell.js";
 import { SandboxPhase, type Sandbox as SandboxModel } from "./generated/datamodel.js";
-import { serviceStatusToJSON } from "./generated/openshell.js";
+
+const decoder = new TextDecoder();
+const EMPTY_BYTES = new Uint8Array();
 
 export interface OpenShellClientOpts {
   /** gRPC gateway endpoint (e.g., "localhost:8080") */
@@ -82,7 +86,7 @@ export class OpenShellClient {
       workdir: request.workdir ?? "",
       environment: request.environment ?? {},
       timeoutSeconds: request.timeoutSeconds ?? 0,
-      stdin: request.stdin ?? new Uint8Array(),
+      stdin: request.stdin ?? EMPTY_BYTES,
     });
   }
 
@@ -114,8 +118,8 @@ export class OpenShellClient {
     command: string[],
     opts?: { workdir?: string; environment?: Record<string, string>; timeoutSeconds?: number },
   ): Promise<ExecCollectResult> {
-    let stdout = "";
-    let stderr = "";
+    const stdoutParts: string[] = [];
+    const stderrParts: string[] = [];
     let exitCode = 0;
 
     for await (const event of this.execSandbox({
@@ -124,15 +128,15 @@ export class OpenShellClient {
       ...opts,
     })) {
       if (event.stdout) {
-        stdout += new TextDecoder().decode(event.stdout.data);
+        stdoutParts.push(decoder.decode(event.stdout.data));
       } else if (event.stderr) {
-        stderr += new TextDecoder().decode(event.stderr.data);
+        stderrParts.push(decoder.decode(event.stderr.data));
       } else if (event.exit) {
         exitCode = event.exit.exitCode;
       }
     }
 
-    return { stdout, stderr, exitCode };
+    return { stdout: stdoutParts.join(""), stderr: stderrParts.join(""), exitCode };
   }
 
   close(): void {

src/stream.ts

@@ -1,5 +1,7 @@
 import type { ExecSandboxEvent } from "./generated/openshell.js";
 
+const decoder = new TextDecoder();
+
 export interface ExecLine {
   type: "stdout" | "stderr";
   line: string;
@@ -27,14 +29,14 @@ export async function* streamExecLines(
 
   for await (const event of grpcStream) {
     if (event.stdout) {
-      stdoutBuf += new TextDecoder().decode(event.stdout.data);
+      stdoutBuf += decoder.decode(event.stdout.data);
       const lines = stdoutBuf.split("\n");
       stdoutBuf = lines.pop() ?? "";
       for (const line of lines) {
         if (line) yield { type: "stdout", line };
       }
     } else if (event.stderr) {
-      stderrBuf += new TextDecoder().decode(event.stderr.data);
+      stderrBuf += decoder.decode(event.stderr.data);
       const lines = stderrBuf.split("\n");
       stderrBuf = lines.pop() ?? "";
       for (const line of lines) {

vitest.config.ts

@@ -2,7 +2,6 @@ import { defineConfig } from "vitest/config";
 
 export default defineConfig({
   test: {
-    globals: true,
     environment: "node",
     include: ["src/__tests__/**/*.test.ts"],
     exclude: ["src/__tests__/integration.test.ts"],