docs(developer-experience): add control-CLI pitfalls to /developer-experience:build-cli #9533

Refs: #9507

Problem

The five pitfalls in #9507 ("Pitfalls for a control CLI") are not in build-cli/reference/cli-contract.md. Line 55 covers only stdout and stderr in general.

Fix

Add rows to the contract, each with an upstream pointer, an as-of date and a recheck trigger:

• A child process inherits the caller's handles and hangs a piped caller. Start the app without inheriting handles.
• A composite command keeps --json stdout to one document and sends sub-step output to stderr.
• The recorded pid may be a wrapper, so find the real app process before attaching.
• Reject unknown flags, repeated step ids, malformed ids and unknown apps or environments fast.
• Name the override mechanism the app actually honors, and never assume environment variables win.

The issue implementer should verify and carry the upstream pointers (the Windows process docs are not on a CI lane fetch host).

Acceptance criteria

• Five new rows in cli-contract.md, each with a pointer, an as-of date and a trigger.
• One eval case: a review of a CLI that pipes a child with inherited handles flags it.
• grep -nE '#[0-9]{3,}' over the changed skill files returns nothing.
• grep -nE '5031|SETWorks|Blazor' over the changed skill files returns nothing (no consumer-specific default).

Blocked by

None.

Files

• plugins/developer-experience/skills/build-cli/reference/cli-contract.md
• plugins/developer-experience/skills/build-cli/evals/evals.json
• Changelog fragment