feat(plugins): add windows-nul-fix plugin to auto-remove problematic nul files

plugins/windows-nul-fix/.claude-plugin/plugin.json

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+{
+  "name": "windows-nul-fix",
+  "version": "1.0.0",
+  "description": "Automatically removes 'nul' files created by Claude Code on Windows when using Git Bash or other Unix-like shells",
+  "author": "Anthropic Community",
+  "homepage": "https://github.com/anthropics/claude-code/issues/4928",
+  "keywords": ["windows", "nul", "fix", "bash", "git-bash"],
+  "platforms": ["windows"]
+}

plugins/windows-nul-fix/README.md

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+# Windows NUL Fix Plugin
+
+Automatically removes problematic `nul` files created by Claude Code on Windows.
+
+## The Problem
+
+When Claude Code runs bash commands on Windows (using Git Bash or similar Unix-like shells), it sometimes uses `2>nul` for stderr redirection. This is Windows CMD syntax, but in Unix shells, it creates a literal file named `nul` instead of redirecting to the null device.
+
+This causes several issues:
+- The `nul` file cannot be easily deleted using Windows Explorer or PowerShell
+- It breaks `git add` and `git commit` operations
+- It can corrupt source control history
+- It appears repeatedly after each bash command
+
+**Related Issue:** [#4928](https://github.com/anthropics/claude-code/issues/4928)
+
+## Solution
+
+This plugin adds a `PostToolUse` hook that automatically removes any `nul` files from the current working directory after each Bash tool execution on Windows.
+
+## Installation
+
+### From Marketplace
+```bash
+claude /plugin install windows-nul-fix
+```
+
+### Manual Installation
+1. Copy the `windows-nul-fix` folder to `~/.claude/plugins/`
+2. Restart Claude Code
+
+## How It Works
+
+```
+PostToolUse (Bash) → remove-nul.js → Delete 'nul' file if exists
+```
+
+The hook:
+1. Only activates on Windows (`os.platform() === "win32"`)
+2. Runs after every Bash tool execution
+3. Checks if a `nul` file exists in the current working directory
+4. Silently removes it if found
+5. Does not interrupt the workflow on errors
+
+## Manual Workarounds
+
+If you prefer not to use this plugin, here are alternative solutions:
+
+### Option 1: Add to .gitignore
+```
+nul
+```
+
+### Option 2: Delete with Git Bash
+```bash
+rm nul
+```
+
+### Option 3: Delete with PowerShell (elevated)
+```powershell
+Remove-Item "\\?\$PWD\nul" -Force
+```
+
+### Option 4: Add to CLAUDE.md
+```markdown
+Windows: use `2>/dev/null` not `2>nul` (causes bash to create literal file)
+```
+
+## Contents
+
+```
+windows-nul-fix/
+├── .claude-plugin/
+│   └── plugin.json      # Plugin metadata
+├── hooks/
+│   └── hooks.json       # PostToolUse hook configuration
+├── scripts/
+│   └── remove-nul.js    # NUL file removal script
+└── README.md            # This file
+```
+
+## Requirements
+
+- Windows operating system
+- Node.js (included with Claude Code)
+
+## License
+
+MIT - See the main Claude Code repository for license details.

plugins/windows-nul-fix/hooks/hooks.json

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+{
+  "description": "Removes 'nul' files created by Claude Code on Windows when bash commands use '2>nul' redirection",
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Bash",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node ${CLAUDE_PLUGIN_ROOT}/scripts/remove-nul.js",
+            "timeout": 5
+          }
+        ]
+      }
+    ]
+  }
+}

plugins/windows-nul-fix/scripts/remove-nul.js

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+#!/usr/bin/env node
+/**
+ * Windows NUL File Remover
+ *
+ * Workaround for https://github.com/anthropics/claude-code/issues/4928
+ *
+ * On Windows, when Claude Code runs bash commands with '2>nul' redirection
+ * (intended for Windows CMD), it creates a literal file named 'nul' instead
+ * of redirecting to the null device. This is because Git Bash and other
+ * Unix-like shells on Windows treat 'nul' as a regular filename.
+ *
+ * This script removes any 'nul' files from the current working directory
+ * after Bash tool execution.
+ */
+
+import { stdin } from "node:process";
+import { rmSync, existsSync } from "node:fs";
+import path from "node:path";
+import os from "node:os";
+
+// Only run on Windows
+if (os.platform() !== "win32") {
+  process.exit(0);
+}
+
+let inputData = "";
+
+stdin.setEncoding("utf8");
+
+stdin.on("data", (chunk) => {
+  inputData += chunk;
+});
+
+stdin.on("end", () => {
+  try {
+    if (!inputData || !inputData.trim().startsWith("{")) {
+      // No valid JSON input, exit silently
+      process.exit(0);
+    }
+
+    const event = JSON.parse(inputData);
+    const cwd = event.cwd || process.cwd();
+    const nulPath = path.join(cwd, "nul");
+
+    // Check if nul file exists and remove it
+    if (existsSync(nulPath)) {
+      rmSync(nulPath, { force: true });
+
+      // Output message for transcript (optional - can be removed for silent operation)
+      // console.log(`Removed 'nul' file from ${cwd}`);
+    }
+
+    process.exit(0);
+  } catch (error) {
+    // Exit silently on errors - don't interrupt the workflow
+    process.exit(0);
+  }
+});
+
+// Handle timeout gracefully
+setTimeout(() => {
+  process.exit(0);
+}, 4000);