Project OpenCode subagents through external WordPress transport

[chubes4]

Closes #362

Summary

• export a bounded, self-contained Agents API graph through argv-safe wp eval
• project embedded instructions, skills, references, policies, and child topology into external OpenCode runtimes
• preserve path-backed local projection while enforcing remote root containment, collision safety, atomic writes, and stale cleanup
• run specialist projection during external profile setup

Verification

• bash tests/opencode-subagents.sh
• bash tests/external-wordpress-runtime.sh
• bash tests/ci-coverage.sh
• syntax checks for every tracked shell script
• PHP lint and Python compilation
• live studio wp eval of the embedded reader against a registered persisted agent

AI assistance

OpenAI gpt-5.6-sol via OpenCode implemented and reviewed the portable projection changes, including runtime-contract verification and security hardening. Chris Huber reviewed and is responsible for every line.