fix: bound the JS endpoint fallback and close small platform gaps

[sunnylqm]

架构审查里剩下的几处小缺陷，每项都以另一端的现有行为为准对齐。

修了什么

• JS 端点回退的请求总数上限为 8。 与原生轮次的 flowcore::kMaxQueryRequests 一致。远程端点列表来自公共镜像，以前没有长度限制，列表很长或被篡改时，每台设备在一次失败的检查里会把所有条目都请求一遍。check-constant-parity 现在把这两个值钉在一起。原有的「失败后重拉一次远程列表」行为保留，相关测试不变。
• 鸿蒙的 buildTime 不再为空。 meta.json 里没有构建时间戳时，回退为应用安装时间，与 iOS 用 Info.plist 修改时间兜底一致。以前 buildTime 为空会让二进制升级同步整个跳过，于是保留 versionName 的应用升级之后，旧热更会继续生效。
• 鸿蒙下载的连接超时改为 15 秒，与 Android 一致；以前等于整个阶段的剩余预算，连不上的镜像会吃掉下一个镜像的时间。readTimeout 仍取剩余 deadline，因为 netstack 把它当作整次传输的超时。
• README 补上 nativeConfigSource，中英文两份选项表都有。另外新增 check-readme-options 并接入 bun lint：ClientOptions 里的选项如果在两份 README 的表格中没有对应行，lint 就会失败。

验证

• bun lint 通过，包括新的选项检查和新增的常量对等检查。两项检查都做过反向验证：去掉 README 新增的那一行，或把上限改成 9，都会报错。
• bun test 437 个用例全部通过，其中新增 2 个请求预算用例。
• 鸿蒙类型检查通过；HAR 的编译由 harmony-build 负责。

🤖 Generated with Claude Code

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Summary by CodeRabbit

• New Features
  • Added the nativeConfigSource option, allowing hosts to retain native update-check configuration without JavaScript overwriting it.
• Improvements
  • Endpoint fallback checks now make no more than eight requests.
  • Downloads use a connection timeout of up to 15 seconds, bounded by the remaining download time.
  • When build-time metadata is unavailable, the app bundle’s modification time can be used instead.

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📥 Commits

Reviewing files that changed from the base of the PR and between 6cc01a5 and 9ab79a1.

📒 Files selected for processing: 2

• src/__tests__/endpoint.test.ts
• src/endpoint.ts

📝 Walkthrough

The changes cap JavaScript endpoint fallback requests at eight, adjust Harmony download timeouts and build-time lookup, and document nativeConfigSource. Lint checks now verify README option coverage, and a parity check compares JavaScript and native request limits.

Changes: Endpoint request budget

Layer / File(s)	Summary
Bound endpoint fallback requests src/endpoint.ts, src/__tests__/endpoint.test.ts, cpp/update_flow_core/native_round.h, scripts/check-constant-parity.js	The fallback accepts a request limit that defaults to eight, deduplicates candidates, skips attempted endpoints, and stops at the limit. Tests cover failed and successful attempts. The parity check compares the JavaScript limit with the native query budget.

Harmony download timeout

Layer / File(s)	Summary
Cap the connection timeout harmony/pushy/src/main/ets/DownloadTask.ts	The connection timeout is capped at 15 seconds or the remaining deadline, whichever is smaller. The read timeout continues to use the full remaining deadline.

Harmony build-time fallback

Layer / File(s)	Summary
Use bundle modification time harmony/pushy/src/main/ets/UpdateContext.ts	When meta.json has no build stamp, getBuildTime caches and returns a positive bundle modification time. Otherwise, it returns an empty string.

Client option documentation

Layer / File(s)	Summary
Document and check client options README.md, README-CN.md, scripts/check-readme-options.js, package.json	Both README option tables document nativeConfigSource. The new lint check verifies that both tables include the keys from ClientOptions.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Suggested reviewers: claude

Merge Risk: 🔵 Low · up to 6cc01

An explicit zero-request limit can still make one endpoint request. The normal client is unaffected, so this is a bounded issue to fix or accept before merging.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 7 files. (3 skipped: 3 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly identifies the primary change by describing the bounded JS endpoint fallback. It also accurately summarizes the related Harmony and documentation fixes as platform gaps.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 7 files. (3 skipped: 3 unsupported.)

✨ Finishing Touches: 💡 1

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @src/endpoint.ts:
- Line 150: Update executeEndpointFallback to check the maxRequests allowance
before calling tryEndpoint, so a limit of zero makes no attempts while positive
limits retain their existing behavior.

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⚙️ Run configuration

• Configuration used: defaults
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📥 Commits

Reviewing files that changed from the base of the PR and between b6cd731 and 6cc01a5.

📒 Files selected for processing: 10

• README-CN.md
• README.md
• cpp/update_flow_core/native_round.h
• harmony/pushy/src/main/ets/DownloadTask.ts
• harmony/pushy/src/main/ets/UpdateContext.ts
• package.json
• scripts/check-constant-parity.js
• scripts/check-readme-options.js
• src/__tests__/endpoint.test.ts
• src/endpoint.ts

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