Pass workspace contract checks to runner

[chubes4]

Summary

• Renames the Docs Agent runner handoff from post_run_workspace_checks to Homeboy's actual workspace_contract_checks reusable workflow input.
• Keeps the bootstrap contract prompt/output generation intact while making the runner-side enforcement reachable.
• Updates bundle validation to assert the correct runner input wiring.

Verification

• php tests/validate-docs-agent-bundle.php
• php tests/repair-docs-links-smoke.php
• actionlint .github/workflows/maintain-docs.yml .github/workflows/docs-agent.yml

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Identified and fixed the Docs Agent/Homeboy reusable workflow input mismatch for human review.