Split runtime-playground command handlers by responsibility

[chubes4]

Goal

Make packages/runtime-playground/src/commands.ts stop being the central dumping ground for Playground command behavior.

Current Problem

commands.ts is still one of the largest source files and mixes multiple responsibilities: WordPress command execution, browser command handling, artifact capture, diagnostics, checks, and command response shaping.

Target Shape

• Keep commands.ts as a small dispatcher/registration layer.
• Move coherent command families into focused modules.
• Preserve all existing command names, inputs, outputs, artifacts, and error behavior.

Candidate Slices

• WordPress/runtime commands.
• Browser/probe commands.
• Artifact/check/diagnostic commands.
• Response/error shaping helpers if they remain mixed into handlers.

Acceptance Criteria

• commands.ts is materially smaller and reads as orchestration, not implementation.
• Each extracted module has one obvious responsibility.
• Existing command registry/discovery/package smokes pass.
• Playground-backed smokes are rerun serially when local port collisions occur.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Drafting this tracker from the current architecture cleanup state.