feat: add command-level CDP overrides / 增加命令级 CDP 覆盖

[coolxll]

Summary / 摘要

This PR adds command-level CDP overrides so browser-backed commands can target different Chrome/Electron sessions without mutating global shell state.

这个 PR 为浏览器相关命令增加了命令级 CDP 覆盖参数，使不同的 Chrome / Electron 会话可以按命令单独指定，而不需要反复切换全局环境变量。

Why / 背景与原因

Today opencli mainly relies on global environment variables such as OPENCLI_CDP_ENDPOINT and OPENCLI_CDP_TARGET.
That works for single-app usage, but it becomes awkward when switching between multiple Electron apps, multiple Chrome instances, or multiple debugging ports.

目前 opencli 主要依赖全局环境变量，例如 OPENCLI_CDP_ENDPOINT 和 OPENCLI_CDP_TARGET。
这种方式在单应用场景下可用，但一旦需要在多个 Electron 应用、多个 Chrome 实例、或者多个调试端口之间切换，就会很不方便。

Typical problems:

• only one active target can be selected through global state
• switching apps requires editing shell state repeatedly
• wrappers become necessary for otherwise simple workflows
• long-running commands such as antigravity serve are harder to route cleanly

典型问题包括：

• 只能通过全局状态选择一个当前目标
• 切换应用需要频繁修改 shell 环境
• 原本简单的工作流不得不额外包一层脚本
• 类似 antigravity serve 这种长运行命令也不容易干净地指定目标

Changes / 修改内容

• add --cdp-endpoint and --cdp-target to browser-backed dynamic commands

• add the same command-level overrides to built-in browser commands such as explore, generate, record, and cascade

• add command-level overrides to opencli antigravity serve

• add runtime helpers to apply and restore CDP env overrides safely during command execution

• update Antigravity docs and skill docs to document per-command usage

• add unit tests for runtime override behavior and Commander integration

• 为浏览器相关的动态命令增加 --cdp-endpoint 和 --cdp-target

• 为 explore、generate、record、cascade 等内建浏览器命令增加同样的命令级覆盖能力

• 为 opencli antigravity serve 增加命令级覆盖能力

• 增加运行时 helper，在命令执行期间安全地设置并恢复 CDP 环境变量

• 更新 Antigravity 文档与技能说明，补充按命令传参的用法

• 增加对应单元测试，覆盖运行时覆盖逻辑和 Commander 接入行为

Example / 示例

opencli antigravity status --cdp-endpoint http://127.0.0.1:9333 --cdp-target Launchpad
opencli antigravity serve --port 8082 --cdp-endpoint http://127.0.0.1:9333 --cdp-target antigravity

This makes multi-app workflows much easier without breaking existing env-based usage.

这样可以在不破坏现有环境变量用法的前提下，显著改善多应用场景下的使用体验。

Verification / 验证

• npm test
• npm run typecheck

[Astro-Han]

Useful feature — per-command CDP overrides solve a real pain point for multi-app workflows. One major concern plus a few smaller items:

Critical

Conflicts with your PR #408

Both PRs define the same exports (BrowserEnvOverrides, withBrowserEnvOverrides, extractBrowserEnvOverrides) with different signatures and modify the same files (cli.ts, runtime.ts, commanderAdapter.ts). They cannot be merged independently — whichever lands second will have type conflicts and likely lose the other's semantics during rebase.

Suggestion: consolidate both PRs into one, with a unified BrowserEnvOverrides type covering cdpEndpoint, cdpTarget, and browserCdp together. The precedence should be: explicit --cdp-endpoint > --browser-cdp auto-discovery > env var default.

Warnings

runtime.test.ts leaks env vars — vi.stubEnv('OPENCLI_CDP_ENDPOINT', ...) is called without afterEach(() => vi.unstubAllEnvs()). This can cause flaky test failures in other suites that depend on these env vars.

No URL validation on --cdp-endpoint — invalid values like foobar are passed directly to the CDP connection layer, producing unfriendly errors. A basic scheme check (http:///ws://) with a clear error message would help.

Option registration repeated 5 times — identical .option('--cdp-endpoint') + .option('--cdp-target') + withBrowserEnvOverrides wrapping in explore, generate, record, cascade, and antigravity serve. Should be extracted into a shared helper (same issue noted in #408).

Non-browser commands also wrapped — commanderAdapter.ts unconditionally calls withBrowserEnvOverrides for all commands. A short-circuit for browser: false commands would avoid the unnecessary async wrapper.

[coolxll]

Superseded by #408. I consolidated the command-level CDP override work into the PR #408 branch so the two changes no longer conflict.