feat(pi-worktree): 新增斜杠命令 git worktree 管理扩展

提供 /wt（别名 /worktree）一键拆分/合并：
- /wt new 建 worktree 后经 SessionManager.forkFrom + switchSession
  迁移会话 cwd，历史上下文保留；合并/切换同理
- /wt merge 先确认再 rebase 到来源分支、默认 --ff-only（可选
  --squash），来源改动用 stash 兜底，冲突可中止或保留后用
  /wt merge --continue / --abort 处理，永不 push
- 来源 checkout 的 .pi/worktree.json 声明环境复刻（copy/link/env/
  postCreate），确认框先展示计划再执行；postCreate 仅在项目已信任
  时以 argv 形式 execFile，失败可 /wt reopen 增量重跑
- 登记文件 <agentDir>/pi-worktree/state.json 原子写入并加锁
  串行化；会话切换后向模型注入 cwd 变更提示；未被 .gitignore
  覆盖的软链/环境文件写入 .git/info/exclude 防止误提交
- 仅注册用户显式触发的斜杠命令，不暴露模型可调用工具

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

pi-worktree/test/state.test.ts

@@ -0,0 +1,151 @@
+import assert from "node:assert/strict";
+import { existsSync } from "node:fs";
+import { mkdir, mkdtemp, realpath, stat, symlink, unlink, utimes, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { dirname, join } from "node:path";
+import test from "node:test";
+
+import {
+	addEntry,
+	findByCwd,
+	findBySlug,
+	loadState,
+	removeEntry,
+	saveState,
+	stateFilePath,
+	updateState,
+	type WorktreeEntry,
+} from "../src/state.ts";
+
+function entry(overrides: Partial<WorktreeEntry> = {}): WorktreeEntry {
+	return {
+		slug: "feat",
+		path: "/nonexistent/path",
+		branch: "wt/feat",
+		sourcePath: "/nonexistent/source",
+		sourceBranch: "main",
+		sourceSha: "0".repeat(40),
+		createdAt: new Date().toISOString(),
+		...overrides,
+	};
+}
+
+test("state roundtrip with owner-only permissions", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const path = join(dir, "pi-worktree", "state.json");
+	const state = await loadState(path);
+	assert.deepEqual(state, { version: 1, worktrees: [] });
+
+	addEntry(state, entry());
+	await saveState(state, path);
+
+	const loaded = await loadState(path);
+	assert.equal(loaded.worktrees.length, 1);
+	assert.equal(loaded.worktrees[0]?.slug, "feat");
+	assert.equal((await stat(path)).mode & 0o777, 0o600);
+	assert.equal((await stat(dirname(path))).mode & 0o777, 0o700);
+
+	removeEntry(loaded, "feat");
+	assert.equal(loaded.worktrees.length, 0);
+	assert.equal(findBySlug(loaded, "feat"), undefined);
+});
+
+test("corrupt or unknown-version state throws instead of overwriting", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const bad = join(dir, "bad.json");
+	await writeFile(bad, "not json{", "utf8");
+	await assert.rejects(() => loadState(bad), /损坏/u);
+
+	const wrongVersion = join(dir, "v2.json");
+	await writeFile(wrongVersion, JSON.stringify({ version: 2, worktrees: [] }), "utf8");
+	await assert.rejects(() => loadState(wrongVersion), /版本不受支持|结构无效/u);
+});
+
+test("findByCwd matches nested subdir via realpath through a symlink", async () => {
+	const root = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const target = join(root, "wt-dir");
+	await mkdir(join(target, "sub", "deep"), { recursive: true });
+	const link = join(root, "link");
+	await symlink(target, link);
+
+	const state = { version: 1 as const, worktrees: [entry({ path: await realpath(target) })] };
+	const found = await findByCwd(state, join(link, "sub", "deep"));
+	assert.equal(found?.slug, "feat");
+	assert.equal(await findByCwd(state, root), undefined);
+});
+
+test("stateFilePath lives under the agent dir, not my-pi", () => {
+	const previous = process.env.PI_CODING_AGENT_DIR;
+	process.env.PI_CODING_AGENT_DIR = join(tmpdir(), "pi-worktree-agentdir-check");
+	try {
+		const path = stateFilePath();
+		assert.equal(path, join(process.env.PI_CODING_AGENT_DIR, "pi-worktree", "state.json"));
+		assert.ok(!path.includes("my-pi"));
+	} finally {
+		if (previous === undefined) delete process.env.PI_CODING_AGENT_DIR;
+		else process.env.PI_CODING_AGENT_DIR = previous;
+	}
+});
+
+test("updateState serializes concurrent mutations without losing entries", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const path = join(dir, "state.json");
+	await Promise.all(
+		Array.from({ length: 20 }, (_, i) =>
+			updateState(
+				(s) => addEntry(s, entry({ slug: `feat-${i}`, branch: `wt/feat-${i}`, path: `/p/${i}` })),
+				path,
+			),
+		),
+	);
+	const loaded = await loadState(path);
+	assert.equal(loaded.worktrees.length, 20);
+	assert.equal(new Set(loaded.worktrees.map((e) => e.slug)).size, 20);
+	assert.equal(existsSync(`${path}.lock`), false);
+});
+
+test("updateState breaks a stale lock older than the stale threshold", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const path = join(dir, "state.json");
+	const lock = `${path}.lock`;
+	await mkdir(dir, { recursive: true });
+	await writeFile(lock, "1 stale", "utf8");
+	const old = new Date(Date.now() - 60_000);
+	await utimes(lock, old, old);
+
+	await updateState((s) => addEntry(s, entry()), path);
+	assert.equal((await loadState(path)).worktrees.length, 1);
+	assert.equal(existsSync(lock), false);
+});
+
+test("updateState does not save when the mutator throws and releases the lock", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const path = join(dir, "state.json");
+	await updateState((s) => addEntry(s, entry()), path);
+
+	await assert.rejects(
+		updateState(() => {
+			throw new Error("boom");
+		}, path),
+		/boom/,
+	);
+	const loaded = await loadState(path);
+	assert.equal(loaded.worktrees.length, 1);
+	assert.equal(existsSync(`${path}.lock`), false);
+});
+
+test("updateState rejects when a fresh lock is held past the timeout", async () => {
+	const dir = await mkdtemp(join(tmpdir(), "pi-worktree-state-"));
+	const path = join(dir, "state.json");
+	const lock = `${path}.lock`;
+	await mkdir(dir, { recursive: true });
+	await writeFile(lock, "1 fresh", "utf8");
+	try {
+		await assert.rejects(
+			updateState(() => undefined, path, { timeoutMs: 300, staleMs: 60_000 }),
+			/状态文件被占用/,
+		);
+	} finally {
+		await unlink(lock).catch(() => undefined);
+	}
+});