docs(code-runtime-python): state the macOS killGroup behavior directly and complete the residual sentence

The review flagged the change-narrative wording 'degrades to the pre-existing
behavior' (prohibited by docs/AGENTS.md) in four spots — README en/zh, the
readProcessStart JSDoc, and the test comment — and the incomplete :77 residual
sentence ('can still' with no verb complement). Reword the four to a direct
statement of current behavior (killGroup signals the pgid without the identity
re-check on macOS), complete the residual sentence with the actual consequence,
and re-record both pairings. Corpus-wide verify-translation-pairing passes 1029.

packages/code-runtime/code-runtime-python/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/code-runtime/code-runtime-python/README.md
-README.md: 25211993e1ebac7b940d4f373391819c15cab5c0
-README.zh.md: ca260b8c8d543545ce927f2c48e4676b34622786
+README.md: fbb37d36523d12357a30c319409afc69ce64e487
+README.zh.md: 10141bc634e523b1fa079280039b0e5eda7e45d8

packages/code-runtime/code-runtime-python/README.md

@@ -36,7 +36,7 @@ No direct invalidation; the named consumer owns any request-prefix changes.
 
 - **The cross-language guard covers executed values and frame field sets, not field types** — `tests/protocol-mirror.e2e.ts` compares `PROTOCOL_FD`, the log truncation marker, and each `TypedDict`'s required and optional fields against a real `python3`. Comparing field types across TypeScript and Python has no mechanical equivalent here, so review plus the backend's real-subprocess suite owns type-level drift.
 - **`RLIMIT_AS` is not enforced on macOS** — the dyld shared cache mapped into every process at exec exceeds any practical address-space cap, and the kernel rejects the `setrlimit` call, so `addressSpaceMb` is skipped there. `cpuSeconds` and `maxWallMs` still bound every run.
-- **PID-reuse protection is inert on macOS** — `readProcessStart` reads `/proc/<pid>/stat`, which Darwin does not provide, so the identity re-check that guards `killGroup` against signalling a recycled pgid always passes there; the guard degrades to the pre-existing behavior rather than paying a `ps` fork on a teardown path. The process-group teardown and the `closeDeadline` bound still contain the run.
+- **PID-reuse protection is inert on macOS** — `readProcessStart` reads `/proc/<pid>/stat`, which Darwin does not provide, so the identity re-check that guards `killGroup` against signalling a recycled pgid always passes there; `killGroup` signals the pgid without the identity re-check on macOS rather than paying a `ps` fork on a teardown path. The process-group teardown and the `closeDeadline` bound still contain the run.
 - **A truncated log's serialized array runs to `maxLogBytes` plus the marker.** The truncation marker is envelope, not payload — it rides uncharged so it can always be emitted — and the outer-array envelope is reserved one byte in the ledger. A truncated run with admitted entries therefore serializes its `logs` array to at most `maxLogBytes + marker + 1`; the marker alone fits any admissible budget (the 64-byte floor guarantees it).
 - **A descendant that calls `setsid()` / `start_new_session=True` escapes teardown.** Termination signals the child's process group with `kill(-pid)`; a descendant that moves itself into a fresh session is no longer in that group and no signal reaches it. If it also releases the inherited stdout/stderr/fd-3 pipes, the leader's `close` still settles the run, and after the `closeDeadline` bound the fiber goes quiescent while that orphan keeps running. This is the containment boundary, not a security one — model code has bash-equivalent trust, and a bash tool can `setsid` away just the same. Reaching such an orphan would require tracking every descendant pid (as the bash-local backend's process-inspector does) and is deferred; the process-group teardown reaps everything that stays in the group.
 - **A combined log-and-value peak is not modelled by the load gate.** Each budget is checked against `addressSpaceMb` on its own. A model daemon thread that keeps writing while the completion value is metered and framed can refill the log pending toward `maxLogBytes` during that window, so the two peaks add in a way no gate admits or rejects. A gate over `(maxLogBytes + maxValueBytes)` was considered and deferred: its discriminating case cannot be scheduled deterministically under `RLIMIT_AS`, so the gate would only prove its own arithmetic. When the combined peak is reached the run dies as `worker-exit` -- containment holds and only the failure classification is degraded.

packages/code-runtime/code-runtime-python/README.zh.md

@@ -36,7 +36,7 @@ host 与 CPython 子进程在子进程的 fd 3 上交换一个无版本号的 JS
 
 - **跨语言 guard 覆盖执行值与帧字段集，但不覆盖字段类型** —— `tests/protocol-mirror.e2e.ts` 使用真实 `python3` 比较 `PROTOCOL_FD`、日志截断标记，以及每个 `TypedDict` 的必填和可选字段。跨 TypeScript 与 Python 比较字段类型在此没有机械等价物，因此类型级漂移由 review 加后端真子进程套件负责。
 - **`RLIMIT_AS` 在 macOS 上不施加** —— 在 exec 时映射进每个进程的 dyld 共享缓存超过任何实际的地址空间上限，内核会拒绝该 `setrlimit` 调用，故 `addressSpaceMb` 在那里被跳过。`cpuSeconds` 与 `maxWallMs` 仍约束每一次运行。
-- **PID 复用防护在 macOS 上失效** —— `readProcessStart` 读取 `/proc/<pid>/stat`，Darwin 不提供它，因此防止 `killGroup` 对已回收的 pgid 发信号的同一性复检在那里恒通过；该防护退化为既有行为，而非在拆卸路径上付出一次 `ps` fork。进程组拆卸与 `closeDeadline` 上界仍约束该次运行。
+- **PID 复用防护在 macOS 上失效** —— `readProcessStart` 读取 `/proc/<pid>/stat`，Darwin 不提供它，因此防止 `killGroup` 对已回收的 pgid 发信号的同一性复检在那里恒通过；`killGroup` 在 macOS 上不经同一性复检直接对 pgid 发信号，而非在拆卸路径上付出一次 `ps` fork。进程组拆卸与 `closeDeadline` 上界仍约束该次运行。
 - **截断日志的序列化数组会到 `maxLogBytes` 加标记为止。** 截断标记是 envelope 而非 payload——它不计费地随行，因此总能发出——而外层数组外壳在账本中预留了一字节。因此带已放行条目的截断运行，其 `logs` 数组序列化后至多为 `maxLogBytes + marker + 1`；标记单独能放进任何可接受的预算（64 字节下限保证这一点）。
 - **调用 `setsid()` ／ `start_new_session=True` 的后代会逃出 teardown。** 终止是用 `kill(-pid)` 向子进程的进程组发信号；一个把自己移入新会话的后代已不在该进程组内，任何信号都到不了它。若它同时释放了继承而来的 stdout／stderr／fd-3 管道，leader 的 `close` 仍会结算该次运行，在 `closeDeadline` 到界之后 fiber 变为完全停稳，而那个孤儿仍在运行。这是 containment 边界，而非安全边界——模型代码具有等同 bash 的信任级别，一个 bash 工具同样能 `setsid` 逃逸。要够到这样的孤儿需要追踪每一个后代 pid（如 bash-local 后端的 process-inspector 所做），此项已推迟；进程组 teardown 会回收所有留在组内的进程。
 - **日志与完成值的叠加峰值未被加载门建模。** 每项预算都是各自对照 `addressSpaceMb` 检查的。模型的 daemon 线程可以在完成值被计量并分帧的窗口内持续写入、把日志 pending 重填到接近 `maxLogBytes`，于是两个峰值以任何门都不曾放行也不曾拒绝的方式相加。对 `(maxLogBytes + maxValueBytes)` 设门的方案经评估后推迟：它的判别用例无法在 `RLIMIT_AS` 之下确定性地构造出来，因此该门只能证明自己的算术。叠加峰值被触及时该次运行死为 `worker-exit`——containment 仍然成立，只是失败分类失真。

packages/code-runtime/code-runtime-python/src/index.ts

@@ -357,9 +357,10 @@ function messageOf(error: unknown): string {
  * Linux reads field 22 of `/proc/<pid>/stat` (starttime in clock ticks); the
  * field is positional after the comm field's closing parenthesis, which is
  * parsed from the LAST such character because a process name may contain one.
- * Darwin has no `/proc`, so the caller gets `undefined` there and the guard
- * degrades to the pre-existing behavior rather than paying a `ps` fork on a
- * teardown path. Any read failure is `undefined` for the same reason: this
+ * Darwin has no `/proc`, so the caller gets `undefined` there and `killGroup`
+ * signals the pgid without the identity re-check rather than paying a `ps`
+ * fork on a teardown path. Any read failure is `undefined` for the same
+ * reason: this
  * hardens a narrow race and must never be the thing that breaks teardown.
  * @param pid - the process to read.
  * @returns its start time, or undefined when unavailable.

packages/code-runtime/code-runtime-python/tests/runtime.spec.ts

@@ -408,8 +408,9 @@ describe('PythonCodeRuntime — process identity', () => {
       // undefined and the guard is inert).
       expect(readProcessStart(0)).toBeUndefined()
     } else {
-      // Darwin has no /proc: the reader reports undefined, and `killGroup` then
-      // keeps its pre-existing behavior instead of paying a `ps` fork per signal.
+      // Darwin has no /proc: the reader reports undefined, and `killGroup`
+      // signals the pgid without the identity re-check instead of paying a `ps`
+      // fork per signal.
       expect(own).toBeUndefined()
     }
   })