新增: Reviewer仲裁+命令互斥锁+冲突解决IPC(批次C散项)

- coordinator: arbitrate_conflicts 方法(规则仲裁:成功方优先/双方成功推荐合并/都失败手动)

- coordinator: ConflictItem 加 subtask_a/subtask_b/recommendation 字段 + ConflictResolution 枚举

- command_lock.rs: CommandLockRegistry (dir+cmd首词 Semaphore 串行化,5个测试全绿)

- resolve_conflict IPC: 解决冲突→更新DB→emit AiConflictResolved 事件闭环

- 3个仲裁测试 + 5个互斥锁测试全绿

- 零编译警告

src-tauri/src/commands/ai/agentic/command_lock.rs

@@ -0,0 +1,134 @@
+//! 命令执行互斥锁 — 防止多 Agent 并行时同目录的同名命令资源竞争
+//!
+//! 设计依据:docs/02-架构设计/专项设计/多Agent并行执行与仲裁合并设计-2026-07-01.md §4.3
+//!
+//! 场景:多 Agent 并行时,两个 SubTask 同时跑 `npm install` 争抢 node_modules。
+//! 方案:按 (working_dir, command_name) 加 mutex,同 key 串行化。
+
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+use tokio::sync::Semaphore;
+
+/// 全局命令锁注册表
+/// key = "{working_dir}::{command_first_word}"
+/// 每个 key 一个 Semaphore(1),同 key 并发请求串行化
+#[allow(dead_code)]
+#[derive(Debug, Clone)]
+pub struct CommandLockRegistry {
+    inner: Arc<Mutex<HashMap<String, Arc<Semaphore>>>>,
+}
+
+impl CommandLockRegistry {
+    #[allow(dead_code)]
+    pub fn new() -> Self {
+        Self {
+            inner: Arc::new(Mutex::new(HashMap::new())),
+        }
+    }
+
+    /// 获取(或创建)指定 key 的信号量。
+    /// 返回 Arc<Semaphore>,调用方 await acquire 后执行命令,drop permit 后释放。
+    #[allow(dead_code)]
+    pub fn get_or_create(&self, working_dir: &str, command: &str) -> Arc<Semaphore> {
+        let cmd_first = command.split_whitespace().next().unwrap_or(command);
+        let key = format!("{}::{}", working_dir, cmd_first);
+        let mut guard = self.inner.lock().unwrap();
+        guard
+            .entry(key)
+            .or_insert_with(|| Arc::new(Semaphore::new(1)))
+            .clone()
+    }
+
+    /// 当前注册的锁数量(调试/监控用)
+    #[allow(dead_code)]
+    pub fn lock_count(&self) -> usize {
+        self.inner.lock().unwrap().len()
+    }
+}
+
+impl Default for CommandLockRegistry {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn lck_01_same_dir_same_cmd_serialized() {
+        let registry = CommandLockRegistry::new();
+        let sem1 = registry.get_or_create("/project", "npm install");
+        let sem2 = registry.get_or_create("/project", "npm install");
+
+        // 同 key 应返回同一个 Semaphore
+        assert!(Arc::ptr_eq(&sem1, &sem2), "同 dir+cmd 应返回同一个 Semaphore");
+
+        // 获取第一个 permit
+        let permit1 = sem1.acquire().await.unwrap();
+        // 第二个应等待(非阻塞测试:try_acquire 应失败)
+        let try_result = sem2.try_acquire();
+        assert!(try_result.is_err(), "同 key 第二个应被阻塞");
+
+        drop(permit1);
+        // 释放后第二个应能获取
+        let permit2 = sem2.acquire().await;
+        assert!(permit2.is_ok(), "释放后应可获取");
+    }
+
+    #[tokio::test]
+    async fn lck_02_different_cmds_parallel() {
+        let registry = CommandLockRegistry::new();
+        let npm_sem = registry.get_or_create("/project", "npm install");
+        let cargo_sem = registry.get_or_create("/project", "cargo build");
+
+        // 不同命令应是不同的 Semaphore
+        assert!(!Arc::ptr_eq(&npm_sem, &cargo_sem), "不同 cmd 应是不同 Semaphore");
+
+        // 两个都能同时获取
+        let p1 = npm_sem.acquire().await.unwrap();
+        let p2 = cargo_sem.acquire().await.unwrap();
+        drop(p1);
+        drop(p2);
+    }
+
+    #[tokio::test]
+    async fn lck_03_different_dirs_parallel() {
+        let registry = CommandLockRegistry::new();
+        let sem1 = registry.get_or_create("/project-a", "npm install");
+        let sem2 = registry.get_or_create("/project-b", "npm install");
+
+        // 不同目录应是不同的 Semaphore
+        assert!(!Arc::ptr_eq(&sem1, &sem2), "不同 dir 应是不同 Semaphore");
+
+        // 两个都能同时获取
+        let p1 = sem1.acquire().await.unwrap();
+        let p2 = sem2.acquire().await.unwrap();
+        drop(p1);
+        drop(p2);
+    }
+
+    #[tokio::test]
+    async fn lck_04_command_extracted_first_word() {
+        let registry = CommandLockRegistry::new();
+        let sem1 = registry.get_or_create("/proj", "npm install --force");
+        let sem2 = registry.get_or_create("/proj", "npm run build");
+
+        // "npm install --force" 和 "npm run build" 首词都是 "npm"
+        // 同 dir + 同首词应串行化
+        assert!(Arc::ptr_eq(&sem1, &sem2), "同 dir+同首词应串行化");
+    }
+
+    #[test]
+    fn lck_05_lock_count_tracks_keys() {
+        let registry = CommandLockRegistry::new();
+        assert_eq!(registry.lock_count(), 0);
+        registry.get_or_create("/a", "npm");
+        assert_eq!(registry.lock_count(), 1);
+        registry.get_or_create("/a", "cargo");
+        assert_eq!(registry.lock_count(), 2);
+        registry.get_or_create("/a", "npm"); // 已存在
+        assert_eq!(registry.lock_count(), 2);
+    }
+}