perf(agent-core-v2): limit config env reads by domain

[huangzheng2016]

Requirement or Bug

Agent turn 中频繁读取单个配置域时，重复计算无关域的环境变量覆盖导致 CPU 开销过高。

Bug Reproduction Steps

1. 用录制响应和工具结果回放 agent turn，不发起模型请求或执行工具。
2. 对回放进程采样 CPU；getEnv 与 applySectionEnvBindings 分别占活跃采样约 16.6% 和 4.2%。
3. 在同一批 40 个 session 上分别运行改动前后代码，各交替运行三轮。

Root Cause

ConfigService.get(domain) 为读取一个域调用 freshEffective()，每次都会检查所有配置域的环境变量绑定。仅两个内置覆盖需要跨域数据；其余域的读取不需要完整计算。这是针对该重复计算的直接修复。

Code Changes

get(domain)
  if memory has domain: return memory value
- compute all effective domains and overlays
+ if every overlay declares that it does not affect domain:
+   apply environment bindings for domain only
+ else:
+   compute all effective domains and overlays

两个内置覆盖声明各自影响的域；未声明影响域的覆盖继续走原来的完整计算路径。

Behavior Changes and Affected Users

行为	之前	之后	依赖旧行为的人群	退路
读取不受覆盖影响的单个配置域	每次检查所有域的环境绑定	只检查目标域的环境绑定	TUI、print、desktop/web、VS Code、ACP、SDK 中运行 agent turn 的用户	自动保留：未声明影响域的覆盖仍走完整路径
读取受覆盖影响的域及实时环境变量更新	完整计算，读取当前环境变量	同样完整计算并读取当前环境变量	使用模型、provider、服务凭证环境变量的用户	不需要

受影响模块：agent-core-v2 配置读取；配置解析、覆盖的返回值和配置文件格式不变。配置测试 130/130 通过，typecheck 和定向 oxlint 通过。六轮共同严格匹配的 81 个 agent、82 个 turn 中，三组候选 turn CPU 总量分别下降 22.6%、18.8%、23.8%；p95 内存增量没有稳定下降。全包测试额外有 15 个与本次配置改动无关的失败，其中 11 个因环境缺少 zip，4 个是 MCP 输出断言。

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue (external PRs: issue must have a maintainer's /approve).
• I have added tests that prove my feature works.
• The behavior-change table above is complete, and every removed behavior or flipped default is named in the changeset and either has an escape hatch or was explicitly approved by a maintainer in this PR.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

[changeset-bot]

🦋 Changeset detected

Latest commit: bd6613d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T14:14:44.601653Z	bd6613d	PR opened

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commit: bd6613d