Keep workspace help and targeted reads bounded

[chubes4]

Summary

• keep nested DMC help side-effect free during WordPress bootstrap
• route workspace show through a targeted bounded child probe instead of broad runtime discovery
• preserve registered remote workspace and context-alias behavior
• add deterministic high-cardinality, timeout-diagnostic, no-mutation, and real CLI-dispatch coverage

Fixes #951.

Verification

• php tests/workspace-command-startup-bounds.php
• PHP syntax checks for all changed PHP files
• git diff --check
• repository-wide for test in tests/*.php; do php "$test" || exit 1; done passes through the new gate, then stops on the unrelated pre-existing autoload failure tracked in Full PHP test loop misses cleanup classifier autoload #952

Homeboy Evidence

• source candidate: cook-data-machine-code-issue-951-lab-20260724-attempt-1-8fe44787
• reviewed correction: cook-data-machine-code-951-review-attempt-2
• reviewed patch SHA-256: bee91b7d8c949297ad92d7f4ea9139869919f82a8dd1cecd4b7bd5f8ed1d8f4e

AI Assistance

• Model: OpenAI GPT-5.6 Sol
• Tool: OpenCode with Homeboy
• Used for: implementation, review correction, deterministic test coverage, artifact promotion, and verification under Chris Huber's direction. Chris remains responsible for every line.