docs(agent): document native wiki interfaces

[changeroa]

Summary

• add the missing Agent-Native StyleGallery guide with its mental model, CLI commands, MCP configuration, resources, mutation boundaries, conformance semantics, protocol projections, and verification commands
• route people and agents to the guide from README, the OKF index, and Consumer Reference
• add the agent-native source-of-truth and lifecycle row to governance
• record the shipped interface in the repository log

Why

PR #29 shipped the implementation but omitted contributor-facing documentation and root navigation. This PR closes that discoverability gap without changing runtime behavior.

Verification

• node scripts/validate-links.mjs --json
• node scripts/validate-ia.mjs --json
• node scripts/validate-governance.mjs --json
• node scripts/validate-okf.mjs --json
• node scripts/validate-domains.mjs --json
• npm run test:agent-native
• git diff --check

All checks passed locally.