fix(gemini): 统一图片附件路径与项目临时目录解析

从技术上，这次改动把 Gemini 图片附件链路补齐到了完整闭环：
- 主进程新增 Gemini 项目 shortId / temp / images 目录解析，兼容 Windows 与 WSL UNC 路径
- 图片保存 IPC 透传 provider、runtime、distro 与项目路径上下文，Gemini 可写入专用临时目录
- 前端发送阶段将 Gemini 图片 Chip 序列化为 CLI 需要的 @path 语法
- 统一图片文件识别逻辑，拖拽、粘贴、手输路径与 @ 选中的图片都按图片附件发送
- 修复 UNC 路径规范化错误压缩前导反斜杠导致的混合分隔符问题

从产品上，Gemini 现在能稳定识别项目级图片附件，不再把图片当普通文件路径发给 CLI，
同时不会影响 Codex / Claude 既有的路径插入与图片保存行为。

测试：
- npm run test

Signed-off-by: Lulu <58587930+lulu-sk@users.noreply.github.com>

Author: lulu-sk

electron/gemini/projectTemp.test.ts

@@ -0,0 +1,115 @@
+import fs from "node:fs";
+import fsp from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import {
+  resolveGeminiImageDirWinPath,
+  resolveGeminiProjectIdentifier,
+  resolveGeminiProjectTempRootWinPath,
+} from "./projectTemp";
+import { getDistroHomeSubPathUNCAsync } from "../wsl";
+
+vi.mock("../wsl", () => ({
+  getDistroHomeSubPathUNCAsync: vi.fn(),
+}));
+
+/**
+ * 中文说明：创建临时测试目录，并确保用例结束后清理。
+ */
+function createTempDir(prefix: string): string {
+  return fs.mkdtempSync(path.join(os.tmpdir(), prefix));
+}
+
+describe("Gemini 项目临时目录解析", () => {
+  const tempDirs: string[] = [];
+
+  afterEach(async () => {
+    try { vi.restoreAllMocks(); } catch {}
+    try { vi.unstubAllEnvs(); } catch {}
+    delete process.env.GEMINI_CLI_HOME;
+    while (tempDirs.length > 0) {
+      const dir = tempDirs.pop();
+      if (!dir) continue;
+      try { await fsp.rm(dir, { recursive: true, force: true }); } catch {}
+    }
+  });
+
+  it("优先读取 projects.json 中已存在的 shortId 映射", async () => {
+    const geminiHome = createTempDir("gemini-home-");
+    tempDirs.push(geminiHome);
+    process.env.GEMINI_CLI_HOME = geminiHome;
+
+    const normalizedProjectRoot = "g:\\projects\\demo";
+    await fsp.mkdir(path.join(geminiHome, "tmp"), { recursive: true });
+    await fsp.writeFile(
+      path.join(geminiHome, "projects.json"),
+      JSON.stringify({ projects: { [normalizedProjectRoot]: "demo-app" } }),
+      "utf8",
+    );
+
+    const projectId = await resolveGeminiProjectIdentifier({
+      projectWinRoot: "G:\\Projects\\demo",
+      runtimeEnv: "windows",
+    });
+
+    expect(projectId).toBe("demo-app");
+  });
+
+  it("registry 缺失时会根据 marker 反查 shortId", async () => {
+    const geminiHome = createTempDir("gemini-home-");
+    tempDirs.push(geminiHome);
+    process.env.GEMINI_CLI_HOME = geminiHome;
+
+    const markerDir = path.join(geminiHome, "tmp", "demo-worktree");
+    await fsp.mkdir(markerDir, { recursive: true });
+    await fsp.writeFile(path.join(markerDir, ".project_root"), "/home/lulu/demo", "utf8");
+
+    const projectId = await resolveGeminiProjectIdentifier({
+      projectWslRoot: "/home/lulu/demo",
+      runtimeEnv: "wsl",
+    });
+
+    expect(projectId).toBe("demo-worktree");
+  });
+
+  it("无 registry/marker 时会按 Gemini slug 规则声明新的 shortId", async () => {
+    const geminiHome = createTempDir("gemini-home-");
+    tempDirs.push(geminiHome);
+    process.env.GEMINI_CLI_HOME = geminiHome;
+
+    const projectId = await resolveGeminiProjectIdentifier({
+      projectWinRoot: "G:\\Projects\\My Demo",
+      runtimeEnv: "windows",
+    });
+
+    expect(projectId).toBe("my-demo");
+    expect(fs.existsSync(path.join(geminiHome, "tmp", "my-demo", ".project_root"))).toBe(true);
+  });
+
+  it("WSL 运行时将 Gemini temp 目录解析为 UNC 路径", async () => {
+    vi.spyOn(os, "platform").mockReturnValue("win32" as any);
+    vi.mocked(getDistroHomeSubPathUNCAsync).mockResolvedValue("\\\\wsl.localhost\\Ubuntu-24.04\\home\\lulu\\.gemini");
+    const originalReadFile = fsp.readFile.bind(fsp);
+    vi.spyOn(fsp, "readFile").mockImplementation(async (targetPath: any, ...args: any[]) => {
+      const normalizedPath = String(targetPath || "");
+      if (normalizedPath === "\\\\wsl.localhost\\Ubuntu-24.04\\home\\lulu\\.gemini\\projects.json")
+        return JSON.stringify({ projects: { "/home/lulu/demo": "demo" } }) as any;
+      return await (originalReadFile as any)(targetPath, ...args);
+    });
+
+    const tempRoot = await resolveGeminiProjectTempRootWinPath({
+      projectWslRoot: "/home/lulu/demo",
+      runtimeEnv: "wsl",
+      distro: "Ubuntu-24.04",
+    });
+    const imageRoot = await resolveGeminiImageDirWinPath({
+      projectWslRoot: "/home/lulu/demo",
+      runtimeEnv: "wsl",
+      distro: "Ubuntu-24.04",
+    });
+
+    expect(tempRoot).toBe("\\\\wsl.localhost\\Ubuntu-24.04\\home\\lulu\\.gemini\\tmp\\demo");
+    expect(imageRoot).toBe("\\\\wsl.localhost\\Ubuntu-24.04\\home\\lulu\\.gemini\\tmp\\demo\\images");
+  });
+});