Implement CLI download logic in node bootstrap

Add download functionality using npm pack and tar extraction for the
Node.js internal bootstrap. Downloads latest CLI version and installs to
DLX directory on first use.

Author: jdalton

src/bootstrap/node.mts

@@ -15,9 +15,15 @@
  */
 
 import { spawn } from 'node:child_process'
-import { existsSync } from 'node:fs'
+import { existsSync, promises as fs } from 'node:fs'
+import path from 'node:path'
 
-import { getCliEntryPoint, getCliPackageDir } from './shared/paths.mjs'
+import {
+  getCliEntryPoint,
+  getCliPackageDir,
+  getCliPackageName,
+  getDlxDir,
+} from './shared/paths.mjs'
 
 /**
  * Check if CLI is installed.
@@ -28,18 +34,94 @@ function isCliInstalled(): boolean {
   return existsSync(entryPoint) && existsSync(packageJson)
 }
 
+/**
+ * Download CLI using npm pack command.
+ * This delegates to npm which handles downloading and extracting the latest version.
+ */
+async function downloadCli(): Promise<void> {
+  const packageName = getCliPackageName()
+  const dlxDir = getDlxDir()
+  const cliDir = getCliPackageDir()
+
+  await fs.mkdir(dlxDir, { recursive: true })
+
+  console.error(`Downloading ${packageName}...`)
+
+  return new Promise((resolve, reject) => {
+    const npmPackProcess = spawn(
+      'npm',
+      ['pack', packageName, '--pack-destination', dlxDir],
+      {
+        stdio: ['ignore', 'pipe', 'inherit'],
+      },
+    )
+
+    let tarballName = ''
+    npmPackProcess.stdout?.on('data', data => {
+      tarballName += data.toString()
+    })
+
+    npmPackProcess.on('error', e => {
+      reject(new Error(`Failed to run npm pack: ${e}`))
+    })
+
+    npmPackProcess.on('exit', async code => {
+      if (code !== 0) {
+        reject(new Error(`npm pack exited with code ${code}`))
+        return
+      }
+
+      try {
+        const tarballPath = path.join(dlxDir, tarballName.trim())
+
+        await fs.mkdir(cliDir, { recursive: true })
+
+        const tarExtractProcess = spawn(
+          'tar',
+          ['-xzf', tarballPath, '-C', cliDir, '--strip-components=1'],
+          {
+            stdio: 'inherit',
+          },
+        )
+
+        tarExtractProcess.on('error', e => {
+          reject(new Error(`Failed to extract tarball: ${e}`))
+        })
+
+        tarExtractProcess.on('exit', async extractCode => {
+          if (extractCode !== 0) {
+            reject(new Error(`tar extraction exited with code ${extractCode}`))
+            return
+          }
+
+          await fs.unlink(tarballPath).catch(() => {
+            // Ignore cleanup errors.
+          })
+
+          console.error('Socket CLI installed successfully')
+          resolve()
+        })
+      } catch (e) {
+        reject(e)
+      }
+    })
+  })
+}
+
 /**
  * Main entry point.
  */
 async function main(): Promise<void> {
   // Check if CLI is already installed.
   if (!isCliInstalled()) {
-    // TODO: Implement download logic using shared utilities.
     console.error('Socket CLI not installed yet.')
-    console.error('Installing from npm...')
-    console.error('TODO: Implement download from npm registry')
-    // eslint-disable-next-line n/no-process-exit
-    process.exit(1)
+    try {
+      await downloadCli()
+    } catch (error) {
+      console.error('Failed to download Socket CLI:', error)
+      // eslint-disable-next-line n/no-process-exit
+      process.exit(1)
+    }
   }
 
   // CLI is installed, delegate to it.