docs(content): add SandBase CLI MCP bridge

[denial123789]

Summary

• add a single source-backed SandBase CLI entry under content/mcp
• document installation, Claude configuration, model discovery and execution workflows
• disclose hosted-service dependency, affiliation, configuration writes, credentials, costs, safety, and privacy behavior
• leave generated README and registry artifacts unchanged

Validation

• pnpm validate:content:strict — passed (1,387 files; only pre-existing warnings)
• git diff --check — passed
• No visual impact

Sources

• https://github.com/sandbaseai/cli
• https://www.sandbase.ai/docs/getting-started/quickstart
• https://www.sandbase.ai/docs/admin/billing

Disclosure: I am affiliated with SandBase, and this contribution was prepared with AI assistance and reviewed against the cited sources.

[denial123789]

The repository policy gate correctly identified that SandBase includes a pay-per-use hosted model gateway and should use the tools/listing flow instead of a direct MCP content PR. Closing this submission rather than rewriting it to evade the commercial routing policy. The affiliation and AI-assistance disclosures remain in the record.