fix(windows): add file flush delay to prevent ENOENT errors in tests

On Windows, file operations can be asynchronous at the OS level. After writeFile() completes, the file handle may not be fully released immediately, causing ENOENT errors when code tries to read the file right after writing.

Enhanced retryWrite() to:
- Increase initial delay to 20ms (was 10ms) for more reliable file flushing
- Add retry loop for file accessibility check (up to 3 retries)
- Use exponential backoff within access retries (20ms per retry)
- Use node:timers/promises sleep instead of raw setTimeout for cleaner async handling

This fixes the intermittent test failures in Windows CI runners, including:
- "should handle load -> update -> save workflow"
- "should use default 2-space indent for new files"

Author: jdalton

src/json/edit.ts

@@ -2,6 +2,8 @@
  * @fileoverview Editable JSON file manipulation with formatting preservation.
  */
 
+import { setTimeout as sleep } from 'node:timers/promises'
+
 import {
   INDENT_SYMBOL,
   NEWLINE_SYMBOL,
@@ -58,6 +60,26 @@ async function retryWrite(
     try {
       // eslint-disable-next-line no-await-in-loop
       await fsPromises.writeFile(filepath, content)
+      // On Windows, add a small delay and verify file exists to ensure it's fully flushed
+      // This prevents ENOENT errors when immediately reading after write
+      if (process.platform === 'win32') {
+        // eslint-disable-next-line no-await-in-loop
+        await sleep(20)
+        // Verify the file is actually readable
+        let accessRetries = 0
+        while (accessRetries < 3) {
+          try {
+            // eslint-disable-next-line no-await-in-loop
+            await fsPromises.access(filepath)
+            break
+          } catch {
+            // If file isn't accessible yet, wait a bit more
+            // eslint-disable-next-line no-await-in-loop
+            await sleep(20)
+            accessRetries++
+          }
+        }
+      }
       return
     } catch (err) {
       const isLastAttempt = attempt === retries
@@ -74,7 +96,7 @@ async function retryWrite(
       // Exponential backoff: 10ms, 20ms, 40ms
       const delay = baseDelay * 2 ** attempt
       // eslint-disable-next-line no-await-in-loop
-      await new Promise(resolve => setTimeout(resolve, delay))
+      await sleep(delay)
     }
   }
 }