Fix runtime package helper late registration

[chubes4]

Summary

• Ensure wp_agent_run_runtime_package() attempts to register the canonical runtime package abilities before reading the Abilities API registry.
• Add regression coverage for the helper path after wp_abilities_api_init has already fired.

Testing

• php -l src/Abilities/functions-ability-dispatch.php
• php tests/runtime-package-run-contract-smoke.php
• composer smoke

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: Root-cause investigation, code change, regression test, and verification.