feat(prd-6): verify workflow triggers and add assignee_trigger (#13)

src/github/utils/image-downloader.ts

@@ -2,6 +2,15 @@ import fs from "fs/promises";
 import path from "path";
 import type { Octokits } from "../api/client";
 
+// Mutable fs reference for cross-platform test compatibility.
+// On Linux, Bun gives test and source files different fs/promises objects,
+// so spyOn(fs, "mkdir") in a test file won't intercept calls here.
+// Tests override these methods directly instead.
+export const _fsForTest = {
+  mkdir: fs.mkdir.bind(fs),
+  writeFile: fs.writeFile.bind(fs),
+};
+
 // Build regexes at call time, reading GITHUB_SERVER_URL from process.env
 // directly. The config.ts export freezes the value at module load time,
 // which can be wrong when the Forgejo CI runner injects its own
@@ -67,7 +76,7 @@ export async function downloadCommentImages(
   const urlToPathMap = new Map<string, string>();
   const downloadsDir = "/tmp/github-images";
 
-  await fs.mkdir(downloadsDir, { recursive: true });
+  await _fsForTest.mkdir(downloadsDir, { recursive: true });
 
   const { imageRegex, htmlImgRegex } = buildImageRegexes();
 
@@ -217,7 +226,7 @@ export async function downloadCommentImages(
           const arrayBuffer = await imageResponse.arrayBuffer();
           const buffer = Buffer.from(arrayBuffer);
 
-          await fs.writeFile(localPath, buffer);
+          await _fsForTest.writeFile(localPath, buffer);
           console.log(`✓ Saved: ${localPath}`);
 
           urlToPathMap.set(originalUrl, localPath);