feat: add SandBase Harness

[liyangbing]

Summary

• add SandBase Harness as a self-hosted AI agent runtime and MCP bridge
• document CLI and MCP access methods
• mark the vendor-submitted entry unverified for maintainer review

Verification

• Official MCP Registry: https://registry.modelcontextprotocol.io/v0.1/servers?search=io.github.sandbaseai%2Fsandbase-harness
• Repository: https://github.com/sandbaseai/sandbase-harness
• Release: https://github.com/sandbaseai/sandbase-harness/releases/tag/v0.3.8

The entry follows CONTRIBUTING.md and keeps verified and featured false for maintainer review.

[vercel]

Someone is attempting to deploy a commit to the assafbar-gmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.

[greptile-apps]

Your trial has ended. Reactivate Greptile to resume code reviews.

[liyangbing]

Maintainer verification context (2026-08-31):

• Current release: https://github.com/sandbaseai/sandbase-harness/releases/tag/v0.3.8
• Official MCP Registry entry: https://registry.modelcontextprotocol.io/v0.1/servers?search=io.github.sandbaseai%2Fsandbase-harness
• Installation and deployment docs: https://github.com/sandbaseai/sandbase-harness/blob/main/docs/installation.md
• MCP bridge configuration: https://github.com/sandbaseai/sandbase-harness/blob/main/docs/mcp-server.md

The listing intentionally keeps verified: false and featured: false; the Vercel message is a preview authorization requirement on the repository owner's project, not a content-validation failure.

[assafbar2]

Merged via #104 — your entry is live in the catalog. This PR conflicted with recent weekly drops on content/changelog.json, so the commit was cherry-picked onto an integration branch with your authorship preserved rather than asking you to rebase. verified was flipped to true after endpoint checks. Thanks for the submission.