fix(codex-wrapper): improve --parallel parameter validation and docs

修复问题:
- codex-wrapper --parallel 模式缺少参数验证,用户误传额外参数导致 shell 解析错误
- 文档中缺少正确 vs 错误用法对比,容易误导用户

主要改进:

1. codex-wrapper/main.go:
   - 添加 --parallel 参数验证 (366-373行)
   - 当检测到额外参数时,输出清晰的错误提示和正确用法示例
   - 更新 --help 文档,添加 --parallel 使用说明

2. skills/codex/SKILL.md:
   - 添加重要提示框,明确 --parallel 只从 stdin 读取配置
   - 新增"正确 vs 错误用法"对比部分,包含3种常见错误示例
   - 修复所有示例中多余的 `-` 参数
   - 在 Delimiter Format 部分强调 workdir 的正确用法

测试验证:
- ✅ 所有单元测试通过
- ✅ 参数验证功能正常
- ✅ 并行执行功能正常
- ✅ 中文内容解析正常

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

codex-wrapper/main.go

@@ -363,6 +363,14 @@ func run() int {
 			printHelp()
 			return 0
 		case "--parallel":
+			if len(os.Args) > 2 {
+				fmt.Fprintln(os.Stderr, "ERROR: --parallel reads its task configuration from stdin and does not accept additional arguments.")
+				fmt.Fprintln(os.Stderr, "Usage examples:")
+				fmt.Fprintln(os.Stderr, "  codex-wrapper --parallel < tasks.txt")
+				fmt.Fprintln(os.Stderr, "  echo '...' | codex-wrapper --parallel")
+				fmt.Fprintln(os.Stderr, "  codex-wrapper --parallel <<'EOF'")
+				return 1
+			}
 			// Parallel mode: read task config from stdin
 			data, err := io.ReadAll(stdinReader)
 			if err != nil {
@@ -888,9 +896,15 @@ Usage:
     codex-wrapper - [workdir]              Read task from stdin
     codex-wrapper resume <session_id> "task" [workdir]
     codex-wrapper resume <session_id> - [workdir]
+    codex-wrapper --parallel               Run tasks in parallel (config from stdin)
     codex-wrapper --version
     codex-wrapper --help
 
+Parallel mode examples:
+    codex-wrapper --parallel < tasks.txt
+    echo '...' | codex-wrapper --parallel
+    codex-wrapper --parallel <<'EOF'
+
 Environment Variables:
     CODEX_TIMEOUT  Timeout in milliseconds (default: 7200000)
 

skills/codex/SKILL.md

@@ -180,11 +180,50 @@ EOF
 
 ### Parallel Execution
 
+> Important:
+> - `--parallel` only reads task definitions from stdin.
+> - It does not accept extra command-line arguments (no inline `workdir`, `task`, or other params).
+> - Put all task metadata and content in stdin; nothing belongs after `--parallel` on the command line.
+
+**Correct vs Incorrect Usage**
+
+**Correct:**
+```bash
+# Option 1: file redirection
+codex-wrapper --parallel < tasks.txt
+
+# Option 2: heredoc (recommended for multiple tasks)
+codex-wrapper --parallel <<'EOF'
+---TASK---
+id: task1
+workdir: /path/to/dir
+---CONTENT---
+task content
+EOF
+
+# Option 3: pipe
+echo "---TASK---..." | codex-wrapper --parallel
+```
+
+**Incorrect (will trigger shell parsing errors):**
+```bash
+# ❌ Wrong: no extra args allowed after --parallel
+codex-wrapper --parallel - /path/to/dir <<'EOF'
+...
+EOF
+
+# ❌ Wrong: --parallel does not take a task argument
+codex-wrapper --parallel "task description"
+
+# ❌ Wrong: workdir must live inside the task config
+codex-wrapper --parallel /path/to/dir < tasks.txt
+```
+
 For multiple independent or dependent tasks, use `--parallel` mode with delimiter format:
 
 **Typical Workflow (analyze → implement → test, chained in a single parallel call)**:
 ```bash
-codex-wrapper --parallel - <<'EOF'
+codex-wrapper --parallel <<'EOF'
 ---TASK---
 id: analyze_1732876800
 workdir: /home/user/project
@@ -207,7 +246,7 @@ EOF
 A single `codex-wrapper --parallel` call schedules all three stages concurrently, using `dependencies` to enforce sequential ordering without multiple invocations.
 
 ```bash
-codex-wrapper --parallel - <<'EOF'
+codex-wrapper --parallel <<'EOF'
 ---TASK---
 id: backend_1732876800
 workdir: /home/user/project/backend
@@ -235,6 +274,8 @@ EOF
 - `workdir: <path>`: Optional, working directory (default: `.`)
   - Best practice: use absolute paths (e.g., `/home/user/project/backend`)
   - Avoids ambiguity and ensures consistent behavior across environments
+  - Must be specified inside each task block; do not pass `workdir` as a CLI argument to `--parallel`
+  - Each task can set its own `workdir` when different directories are needed
 - `dependencies: <id1>, <id2>`: Optional, comma-separated task IDs
 - `session_id: <uuid>`: Optional, resume a previous session
 - `---CONTENT---`: Separates metadata from task content
@@ -249,7 +290,7 @@ EOF
 **Resume Failed Tasks**:
 ```bash
 # Use session_id from previous output to resume
-codex-wrapper --parallel - <<'EOF'
+codex-wrapper --parallel <<'EOF'
 ---TASK---
 id: T2
 session_id: 019xxx-previous-session-id