test(core): align Vertex auth test with content interface

[yu-xin-c]

What this PR does

Updates the remaining Vertex auth lazy-construction test to exercise embedContent, the same surviving ContentGenerator operation used by the rest of the #9676 test migration.

Why it's needed

#9676 removed countTokens from ContentGenerator, but a Vertex ADC test added independently on main retained one generator.countTokens(...) call. As a result, current main fails during npm ci, build, and typecheck with TS2339 at contentGenerator.test.ts:776. The PR's own sandboxed verification had already captured the integration failure here.

Reviewer Test Plan

How to verify

1. On current main, run npm run build --workspace packages/core and observe Property 'countTokens' does not exist on type 'ContentGenerator'.
2. On this branch, run cd packages/core && npx vitest run src/core/contentGenerator.test.ts --maxWorkers=1 and confirm all 27 tests pass.
3. Run npm run typecheck and confirm every workspace plus typecheck:integration passes.

Evidence (Before & After)

N/A for UI. Before: core compilation stops at contentGenerator.test.ts:776 with TS2339. After: the full repository build completes during npm ci, the focused file passes 27/27, and workspace plus integration typecheck completes successfully.

Tested on

OS	Status
🍏 macOS	✅
🪟 Windows	N/A
🐧 Linux	N/A

Environment (optional)

Node.js 22.22.2 on macOS. Verified with a clean npm ci, which completed the full prepare/build pipeline.

Risk & Scope

• Main risk or tradeoff: None beyond changing which retained API initializes the mocked Gemini client in this test.
• Not validated / out of scope: Production behavior and unrelated refactor(core): shrink the content generator interface #9676 follow-up suggestions.
• Breaking changes / migration notes: None; this is test-only and restores the build after the interface shrink.

Linked Issues

Follow-up to #9676.

中文说明

本 PR 的改动

将遗漏的 Vertex 认证懒构造测试改为调用 embedContent；这是 #9676 其余测试迁移统一采用、且仍保留在 ContentGenerator 中的操作。

为什么需要

#9676 从 ContentGenerator 删除了 countTokens，但 main 上独立加入的一条 Vertex ADC 测试仍保留 generator.countTokens(...)。因此当前 main 在 npm ci、build 和 typecheck 阶段都会于 contentGenerator.test.ts:776 报出 TS2339。该集成失败此前也已被该 PR 自身的沙箱验证记录。

审查测试计划

验证方法

1. 在当前 main 上运行 npm run build --workspace packages/core，可看到 Property 'countTokens' does not exist on type 'ContentGenerator'。
2. 在本分支运行 cd packages/core && npx vitest run src/core/contentGenerator.test.ts --maxWorkers=1，确认 27 条测试全部通过。
3. 运行 npm run typecheck，确认所有 workspace 与 typecheck:integration 均通过。

前后证据

UI 不适用。修改前：core 编译在 contentGenerator.test.ts:776 因 TS2339 中止。修改后：干净 npm ci 中的全仓库 build 完成，目标文件 27/27 通过，全工作区与 integration typecheck 成功完成。

测试平台

OS	状态
🍏 macOS	✅
🪟 Windows	N/A
🐧 Linux	N/A

环境（可选）

macOS，Node.js 22.22.2。已通过干净 npm ci 验证，它完整执行并通过了 prepare/build 流程。

风险与范围

• 主要风险或取舍：除测试中改用另一个仍保留的 API 来初始化 Gemini mock 客户端外，无其他风险。
• 未验证 / 范围外：生产行为及 refactor(core): shrink the content generator interface #9676 的其他后续建议。
• 破坏性变更 / 迁移说明：无；这是纯测试修复，用于恢复接口收缩后的构建。

关联问题

#9676 的后续修复。

[qwen-code-ci-bot]

✅ Qwen Triage finished — view run. See the stage comments in this thread for the result.

✅ Qwen Triage 已完成 —— 查看运行。结果见本线程中的各阶段评论。

[qwen-code-ci-bot]

Thanks @yu-xin-c — your diagnosis was right: main really was broken at contentGenerator.test.ts:776 (TS2339, the leftover countTokens call after #9676). But the identical fix landed first: #9888 merged the exact same change at 09:24 UTC today (main commit 6a21c43), about 15 minutes before this PR was opened.

Verified via the API:

• This PR's diff is byte-for-byte identical to #9888's diff — same file, same hunks, same blobs (a2082a09d3e → 4e1831f4336).
• The file blob on this PR's head (4e1831f4336d…) already matches the same file on main — merging this PR would change nothing.

So there is nothing left to review or test here. Requesting changes only because the gate needs a formal state; the right outcome is closing this PR as superseded by #9888. Thanks for catching the broken build and taking the time to fix it — you were only minutes late. 🙏

中文说明

感谢 @yu-xin-c —— 你的判断是对的：main 当时确实因 contentGenerator.test.ts:776 的 TS2339（#9676 之后遗留的 countTokens 调用）而构建失败。但相同的修复先一步落地：#9888 已于今天 09:24 UTC 合并了完全一致的改动（main commit 6a21c43），比本 PR 的创建时间早约 15 分钟。

已通过 API 核实：

• 本 PR 的 diff 与 #9888 逐字节一致——同一文件，同一 hunk，同一 blob（a2082a09d3e → 4e1831f4336）。
• 本 PR head 上该文件的 blob（4e1831f4336d…）与 main 上的已完全相同——合并本 PR 不会产生任何变化。

因此这里没有可继续审查或测试的内容。标记 request changes 只是流程需要一个正式状态；正确的处理是关闭本 PR（已被 #9888 取代）。感谢你发现构建损坏并花时间修复——只是晚了几分钟。🙏

— Qwen Code · qwen3.8-max

[yu-xin-c]

Thanks for confirming and for tracing this to #9888. I independently hit the same TS2339 failure while validating #9896 and opened this fix before noticing that #9888 had landed minutes earlier. Closing as superseded by #9888.