test(cli): Write CLI tools test suite

[coderooz]

Write comprehensive tests for CLI command execution tools. Create tests/cli-tools-test.js using node:test runner.

Test areas:

• run_command: basic execution, background mode, timeout
• get_command_output: output retrieval, offset handling
• list_processes: status filtering
• kill_process: SIGTERM, SIGKILL
• blocked commands: destructive patterns rejected
• max concurrent processes
• output buffering truncation
• CWD validation (within project root)
• process lifecycle: running, completed, failed, killed

Safe test commands: echo, node -e console.log, sleep/timeout

Depends on: CLI registration (#43)
Milestone: v2.7.0