fix: delete existing file before download to prevent corruption

CI caching can restore partial/corrupted downloads that cause
extraction failures. Delete any existing file before starting
the download to ensure a clean state.

Author: jdalton

src/http-request.ts

@@ -14,6 +14,8 @@
  * - Zero dependencies on external HTTP libraries.
  */
 
+import { safeDelete } from './fs.js'
+
 let _fs: typeof import('node:fs') | undefined
 
 /**
@@ -918,6 +920,13 @@ export async function httpDownload(
     }
   }
 
+  // Delete existing file before download to prevent partial/corrupted file issues.
+  // CI caching can restore partial downloads that cause extraction failures.
+  const fs = getFs()
+  if (fs.existsSync(destPath)) {
+    await safeDelete(destPath)
+  }
+
   // Retry logic with exponential backoff
   let lastError: Error | undefined
   for (let attempt = 0; attempt <= retries; attempt++) {

src/releases/github.ts

@@ -313,6 +313,7 @@ export async function downloadReleaseAsset(
   await safeMkdir(path.dirname(outputPath))
 
   // Download using httpDownload which supports redirects and retries.
+  // httpDownload deletes existing files before downloading to prevent partial/corrupted issues.
   await httpDownload(downloadUrl, outputPath, {
     logger: quiet ? undefined : logger,
     progressInterval: 10,