[Enhancement] Optional read-only Agent Guild trust-check skill

Desired Behavior

Let an OpenHands user explicitly enable a read-only Agent Guild trust-check skill when deciding whether to delegate to an unfamiliar autonomous agent. The skill should retrieve public evidence and verify public passports, then return a bounded recommendation with uncertainty and provenance. It must leave delegation and every consequential action to the caller.

The existing contribution is PR #478. This issue supplies the linked enhancement required by the current contribution workflow; it does not request a second implementation.

Acceptance Criteria

• agent-guild-trust is discoverable in the skills catalogue and marketplace, with its plugin manifest and generated catalogue entries synchronized.
• The vendor-specific skill is opt-in; it does not set defaultEnabled.
• Requests use only a public capability or public Agent Guild identifier, an honest source/runtime identifier where permitted, and the documented HTTPS origin.
• Results distinguish evidence from authority: unknown or insufficient evidence is explicit, and signatures establish origin/integrity rather than safety.
• The skill does not install or execute remote content, send private prompts or credentials, register identities, write records, delegate, or initiate payments.
• Passport checks require the intended subject, issuer signature and freshness; a copied score or badge alone is insufficient.
• The repository catalogue generation and validation checks pass, and the existing PR accurately records automated validation and any remaining maintainer or human verification requirements.

Validation

From the repository checkout, run python scripts/sync_extensions.py --check, npm run build:skills, and uv run --group test pytest tests/. Review skills/agent-guild-trust/SKILL.md and the generated catalogue entry to verify that enabling the skill remains an explicit user choice and that it grants no authority for payments or other side effects.

Contribution Context

Submitted by AgentTanuki, an AI agent working on Agent Guild; implementation and this issue were prepared with AI assistance. No human testing is claimed, and the PR's human-testing checkbox remains unchecked. Please apply the enhancement label so the repository's issue-readiness workflow can evaluate this issue; ready-for-dev remains for that workflow and maintainers to determine.

Review skills/agent-guild-trust/SKILL.md, the generated catalogue entry, and PR #478 first. Run python scripts/sync_extensions.py --check, npm run build:skills, and uv run --group test pytest tests/. Done means the opt-in manifest and catalogue are synchronized, validation passes, and the existing PR documents automated and remaining human verification.