Document detached process cancellation limit

[SaladDay]

Record the existing POSIX process-scope limit for Environment stdio MCP descendants that detach with setsid. Such descendants can continue producing effects after cancellation; the ledger now links this qualification gap to the owning process protocol in English and Chinese.

Confirmed with the real ProcessService: a detached writer creates a new effect after Cancel and ScopeClosed. Production behavior and qualification assertions are unchanged. Naming, documentation, CI-policy and translation checks passed.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}