test(ios): close T-iOS-32's end-to-end half — real worktree lifecycle against a real server

T-iOS-32's acceptance is "builder 测试 + 端到端一次". The builder half was green,
but grep for projects/worktree across the whole test tree returned nothing — no
test had ever created or removed a real git worktree against a real server.

Six tests on a throwaway git fixture: create/remove/prune verified against both
the filesystem and git's own `worktree list --porcelain` + .git/worktrees/, and
asserting the values the SERVER derives rather than echoing our input (branch
feature/e2e-worktree becomes directory feature-e2e-worktree; the raw branch name
must never appear in the path). Includes a differential leg for the guarded-route
rule — the same request without Origin is 403 with zero side effects, and with it
is 200 — which needs raw URLSession, since APIClient structurally cannot emit an
Origin-less guarded request.

GET /sessions gets its own HOME-isolated server: history.ts reads
os.homedir()/.claude/projects, so against the shared harness the assertions would
land on the developer's real Claude history, and in CI the directory is absent so
it degrades to [] and proves nothing.

Integration tests 26 -> 32, independently re-run.

ios/IntegrationTests/GitFixture.swift

@@ -0,0 +1,155 @@
+//
+// GitFixture.swift — T-iOS-32 端到端腿的**一次性 git 仓库**夹具
+//
+// 为什么必须是自建的临时仓库：`POST /projects/worktree` 是全应用**唯一**真正
+// 写盘的功能，服务器会在 `<dirname(repo)>/<basename(repo)>-worktrees/` 下真建
+// 目录、真开分支（src/http/worktrees.ts:146-160,224-256）。把它指向用户自己的
+// 仓库 = 在别人的工作区里留垃圾分支/目录。所以夹具把 repo **和**它派生出来的
+// worktree 根一起关在同一个临时目录里，`destroy()` 一把删干净。
+//
+// 布局（worktreeBase 的算法与服务端逐字对应，不是猜的）：
+//   <root>/repo                      ← 夹具仓库（一次空提交，HEAD 可用）
+//   <root>/repo-worktrees/<sanitized> ← 服务器自己算出来的 worktree 目录
+//
+// 所有断言都拿 **git 自己**的 `worktree list --porcelain` 当第二信源：只信
+// HTTP 响应体的话，"服务器说建好了" 和 "盘上真建好了" 就分不开。
+
+import Darwin
+import Foundation
+
+/// `git worktree list --porcelain` 里的一条记录（只留断言用得上的字段）。
+struct RegisteredWorktree: Sendable, Equatable {
+    let path: String
+    let branch: String?
+    /// git 自己标记的"目录没了、登记还在"（`prunable <reason>`）。
+    let prunable: Bool
+}
+
+/// 跑一条 git 命令并返回合并后的输出；非零退出码抛 `HarnessError.setup`
+/// （夹具失败必须**响亮**，绝不能静默变成一条"断言不成立"）。
+@discardableResult
+func runGit(_ arguments: [String], in directory: URL) throws -> String {
+    let process = Process()
+    process.executableURL = URL(fileURLWithPath: "/usr/bin/git")
+    process.arguments = arguments
+    process.currentDirectoryURL = directory
+    let pipe = Pipe()
+    process.standardOutput = pipe
+    process.standardError = pipe
+    var environment = ProcessInfo.processInfo.environment
+    environment["GIT_TERMINAL_PROMPT"] = "0" // 夹具永远不联网、永远不问密码
+    process.environment = environment
+    try process.run()
+    // 先读到 EOF 再 wait：反过来会在输出撑满管道缓冲时死锁。
+    let data = pipe.fileHandleForReading.readDataToEndOfFile()
+    process.waitUntilExit()
+    let text = String(decoding: data, as: UTF8.self)
+    guard process.terminationStatus == 0 else {
+        throw HarnessError.setup(
+            "git \(arguments.joined(separator: " ")) 退出码 \(process.terminationStatus): \(text)")
+    }
+    return text
+}
+
+/// 一个临时目录里的一次性 git 仓库。值语义 + 显式 `destroy()`（用例 `defer` 调）。
+struct GitFixture: Sendable {
+    /// 临时根目录，**已解 symlink**（macOS 的 $TMPDIR 是 /var/… → /private/var/…；
+    /// 不解的话服务端 realpath 之后返回的路径与我们手上的字符串对不上）。
+    let root: URL
+    /// 夹具仓库本体（`<root>/repo`）。
+    let repo: URL
+
+    /// 服务端在 `worktreeRoot` 未配置时算出来的 worktree 根：
+    /// `<dirname(repo)>/<basename(repo)>-worktrees`（src/http/worktrees.ts:151-152）。
+    var worktreeBase: URL { root.appending(path: "\(repo.lastPathComponent)-worktrees") }
+
+    /// 提交身份走 `-c`：不读、不写用户的全局 git 配置，也不触发 gpg 签名。
+    private static let identity = [
+        "-c", "user.email=fixture@example.invalid",
+        "-c", "user.name=WebTerm Fixture",
+        "-c", "commit.gpgsign=false",
+    ]
+
+    /// 建仓 + 一次空提交（`git worktree add` 在 unborn HEAD 上会失败，所以必须有）。
+    static func make() throws -> GitFixture {
+        let manager = FileManager.default
+        let raw = manager.temporaryDirectory
+            .appending(path: "webterm-worktree-e2e-\(UUID().uuidString)")
+        try manager.createDirectory(at: raw, withIntermediateDirectories: true)
+        // 一次性钉成规范形式（macOS 的 $TMPDIR 是 /var/… → /private/var/…）。服务端
+        // 拿到的就是规范路径，它算出来的 worktree 目录、git 报回来的路径三者同形。
+        let root = URL(fileURLWithPath: canonicalPath(raw.path), isDirectory: true)
+        let repo = root.appending(path: "repo")
+        try manager.createDirectory(at: repo, withIntermediateDirectories: true)
+        try runGit(["-c", "init.defaultBranch=main", "init", "-q"], in: repo)
+        try runGit(identity + ["commit", "-q", "--allow-empty", "-m", "fixture"], in: repo)
+        return GitFixture(root: root, repo: repo)
+    }
+
+    /// 尽力而为的清理：repo 与它的 worktree 根都在 `root` 底下，一把删完。
+    /// 吞错是刻意的 —— 清理失败只留一个临时目录，不该把用例判定改写掉。
+    func destroy() {
+        try? FileManager.default.removeItem(at: root)
+    }
+
+    // ── 第二信源：git 自己的登记 ────────────────────────────────────────────
+
+    /// 解析 `git worktree list --porcelain`（空行分隔的记录，首条是主 worktree）。
+    func registeredWorktrees() throws -> [RegisteredWorktree] {
+        let porcelain = try runGit(["worktree", "list", "--porcelain"], in: repo)
+        var out: [RegisteredWorktree] = []
+        var path: String?
+        var branch: String?
+        var prunable = false
+        func flush() {
+            guard let path else { return }
+            out.append(RegisteredWorktree(path: path, branch: branch, prunable: prunable))
+            (branch, prunable) = (nil, false)
+        }
+        for rawLine in porcelain.split(separator: "\n", omittingEmptySubsequences: false) {
+            let line = String(rawLine)
+            if line.isEmpty {
+                flush()
+                path = nil
+                continue
+            }
+            if line.hasPrefix("worktree ") {
+                path = String(line.dropFirst("worktree ".count))
+            } else if line.hasPrefix("branch refs/heads/") {
+                branch = String(line.dropFirst("branch refs/heads/".count))
+            } else if line == "prunable" || line.hasPrefix("prunable ") {
+                prunable = true
+            }
+        }
+        flush()
+        return out
+    }
+
+    /// 按规范路径找一条登记（symlink 别名与规范路径必须算同一个）。
+    func registeredWorktree(atCanonicalPath target: String) throws -> RegisteredWorktree? {
+        let wanted = canonicalPath(target)
+        return try registeredWorktrees().first { canonicalPath($0.path) == wanted }
+    }
+
+    /// `.git/worktrees/` 下的行政登记目录名（prune 要清掉的正是这些）。
+    func administrativeEntries() -> [String] {
+        let dir = repo.appending(path: ".git/worktrees")
+        let names = try? FileManager.default.contentsOfDirectory(atPath: dir.path)
+        return (names ?? []).sorted()
+    }
+}
+
+/// 规范绝对路径 = `realpath(3)`；路径不存在时**原样返回**。
+///
+/// 为什么不能用 `URL.resolvingSymlinksInPath()`（实测踩过，本文件的 RED 就是它）：
+/// 它的文档行为是「若路径以 /private 开头就**去掉** /private」，方向正好相反 ——
+/// 于是夹具根停在 `/var/folders/…`，而 git 的 `worktree list` 报的是
+/// `/private/var/folders/…`。更糟的是那层转换**依赖路径是否存在**：目录被删掉之后
+/// `/private` 不再被剥离，于是"删干净了吗"这类断言会因为路径形状而不是因为事实
+/// 失败。`realpath(3)` 只做一个方向（→ 规范形式），夹具在建立时就把根钉成规范形式，
+/// 此后所有比较都是纯字符串相等，与"路径此刻还存不存在"无关。
+func canonicalPath(_ path: String) -> String {
+    guard let resolved = realpath(path, nil) else { return path }
+    defer { free(resolved) }
+    return String(cString: resolved)
+}