fix(cli): bound diagnostics and add swap management

scripts/src/command.ts

@@ -1,5 +1,5 @@
 import { spawn, spawnSync } from "node:child_process";
-import { createWriteStream, existsSync, readFileSync } from "node:fs";
+import { closeSync, createWriteStream, existsSync, openSync, readSync, statSync } from "node:fs";
 
 export interface CommandResult {
   command: string[];
@@ -7,20 +7,26 @@ export interface CommandResult {
   exitCode: number | null;
   stdout: string;
   stderr: string;
+  signal: NodeJS.Signals | null;
+  timedOut: boolean;
 }
 
-export function runCommand(command: string[], cwd: string): CommandResult {
+export function runCommand(command: string[], cwd: string, options: { timeoutMs?: number } = {}): CommandResult {
   const result = spawnSync(command[0], command.slice(1), {
     cwd,
     encoding: "utf8",
     maxBuffer: 1024 * 1024 * 8,
+    timeout: options.timeoutMs,
   });
+  const error = result.error as (Error & { code?: string }) | undefined;
   return {
     command,
     cwd,
     exitCode: result.status,
     stdout: result.stdout ?? "",
-    stderr: result.stderr ?? result.error?.message ?? "",
+    stderr: result.stderr ?? error?.message ?? "",
+    signal: result.signal,
+    timedOut: error?.code === "ETIMEDOUT",
   };
 }
 
@@ -50,6 +56,16 @@ export async function runCommandToFiles(command: string[], cwd: string, stdoutFi
 
 export function tailFile(path: string, maxBytes = 8192): string {
   if (!existsSync(path)) return "";
-  const content = readFileSync(path);
-  return content.subarray(Math.max(0, content.length - maxBytes)).toString("utf8");
+  const safeMaxBytes = Math.max(0, Math.floor(maxBytes));
+  if (safeMaxBytes === 0) return "";
+  const size = statSync(path).size;
+  const bytesToRead = Math.min(size, safeMaxBytes);
+  const buffer = Buffer.alloc(bytesToRead);
+  const fd = openSync(path, "r");
+  try {
+    readSync(fd, buffer, 0, bytesToRead, size - bytesToRead);
+  } finally {
+    closeSync(fd);
+  }
+  return buffer.toString("utf8");
 }