feat(antigravity): add safetySettings controls and payload inspector

[Tungnamh9231]

中文

这个 PR 主要补两个我在调 Antigravity 请求时一直缺的东西：按模型控制 safetySettings，以及在控制面板里直接看到最终真正发出去的请求体。

safetySettings

目前仓库已经会按普通模型 / Lite 模型生成不同的 safety category，但没有地方控制这些内容最终要不要发、用什么 threshold，也不好处理某些模型对 category 支持不一致的情况。

这次在桌面版和移动版控制面板的 Antigravity 兼容设置里，放在 Antigravity切换凭证 后面加了一个 Antigravity safetySettings 兼容性控制 面板。

可以做这些事：

• 全局决定是否发送 safetySettings，threshold 支持 BLOCK_NONE / OFF
• 给单独的 canonical model 加 override：整个字段不发，或者只排除指定 category
• 模型列表直接用 Antigravity fetchAvailableModels 的结果，不另外维护一份模型表
• Lite 模型本身不支持的 category 会标红并锁住，避免误以为还能发送
• 已经保存的模型即使暂时不在 fetchAvailableModels 里也不会被自动删掉
• 规则多于一条时改成局部滚动，并加了已添加模型搜索，避免配置页越拉越长

默认仍然保持原来的行为：这个功能没有开启时，最终请求里不会带 safetySettings。开启后也继续复用仓库现有的 Default / Lite category 列表，没有再造一套 category 来源。

规则是在 Antigravity 请求最终发送前应用的，所以抗截断、假流式这类本地 model 变体最终还是跟实际发送的 canonical model 使用同一条规则。过滤完一个 category 都不剩时会直接省略字段，不会发 safetySettings: []。

Safety 配置现在也跟其它设置一样，直接合并到公共 saveConfig()，通过同一个 /config/save 保存，没有再对全局 window.fetch 做额外包装。

请求体检查

另外在日志筛选里加了一个 请求体检查。

Antigravity 每次真正执行 stream / non-stream HTTP 请求前，会把当次实际使用的 final_payload 记成一条 [PAYLOAD] 日志。这样调 model mapping、safety rule、project 切换、tool config 之类的问题时，可以直接确认最后送到 provider 的 JSON 到底是什么。

这里记录的是 JSON body，不记录 Authorization header。[PAYLOAD] 在控制面板里单独显示，不混进普通的 All / Info / Warning；contents 会按 message / parts 展开，长对话会比一整行 JSON 好看一些。实时日志会先把跨多个 8KB 读取块的长 payload 拼成完整一行再发给前端，避免半截 JSON 只能刷新后才正常显示。

我把改动尽量限制在 Antigravity 请求和控制面板相关代码，默认不开 safetySettings 时不会改变原有请求行为。

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English

This PR adds two things that were missing when debugging Antigravity requests: per-model safetySettings control and a way to inspect the actual final request body sent to the provider.

safetySettings

The repo already builds different safety category lists for regular and Lite models, but there was no way to control whether those settings are sent, which threshold is used, or how to handle models that do not support the same set of categories.

I added an Antigravity safetySettings panel to the Antigravity compatibility settings section in both desktop and mobile control panels, directly after the existing Antigravity switch credential option.

The panel allows you to:

• enable/disable sending safetySettings globally and choose BLOCK_NONE or OFF
• add overrides for a canonical model, either omitting the whole field or filtering selected categories
• use the model list returned by Antigravity fetchAvailableModels instead of maintaining another model list
• show Lite-only incompatibilities as locked/red categories so they are not mistaken for sendable settings
• keep saved rules for models that temporarily disappear from fetchAvailableModels
• use a local scroll area and search box once multiple model rules are added, so the settings page does not keep growing

The default behavior stays unchanged: when the feature is not enabled, safetySettings is omitted from the final request. When enabled, it reuses the existing Default / Lite category lists already in the repo rather than introducing another source of safety categories.

Rules are applied right before the final Antigravity request is built, so local model variants such as anti-truncation or pseudo-streaming still follow the rule for the canonical model that is actually sent upstream. If filtering removes every category, the field is omitted instead of sending safetySettings: [].

Safety settings are saved the same way as the rest of the control-panel config now: they are merged into the existing saveConfig() payload and sent through the same /config/save request. There is no global window.fetch wrapping involved.

Request body inspector

I also added a 请求体检查 entry to the log filter.

Right before each real Antigravity stream or non-stream HTTP request, the exact final_payload used for that attempt is logged with a [PAYLOAD] marker. This makes it much easier to check the final JSON after model mapping, safety filtering, project switching, tool config, and the other provider-boundary changes have already been applied.

Only the JSON body is logged; the Authorization header is not included. In the control panel, payload entries are kept out of the normal All / Info / Warning views, and contents is expanded by message / parts so multi-turn payloads are easier to read. For live logs, payload lines spanning multiple 8KB reads are buffered until the complete line is available, so the frontend never receives half of a JSON payload and only formats it correctly after a reload.

The changes are scoped to the Antigravity request path and control panel, and the existing request behavior remains unchanged unless the new safetySettings option is enabled.