docs(plugins): 标注 driver-mongodb 仅支持单租户 (#3724)

The package catalog's "When to use" line advertised the Mongo driver for any
"existing MongoDB infrastructure" with no mention that it cannot isolate
tenants and now refuses to boot outside a `single` tenancy posture. Flagged by
the docs-drift check on this PR.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014Hk4hSCirLNWLkgkNkj8YT

Author: claude

content/docs/plugins/packages.mdx

@@ -185,7 +185,8 @@ const driver = new SqliteWasmDriver({ filename: ':memory:' });
 **MongoDB Driver** — Document-oriented storage backend.
 
 - **Purpose**: Native MongoDB driver for ObjectQL with document-flavored objects
-- **When to use**: Existing MongoDB infrastructure, document-shaped data
+- **When to use**: Existing MongoDB infrastructure, document-shaped data — **single-tenant deployments only**
+- **Not supported**: row-level tenant isolation. The driver refuses to boot when the tenancy posture is not `single` — see [Drivers → Multi-tenancy](/docs/data-modeling/drivers#multi-tenancy-not-supported)
 - **README**: [View README](https://github.com/objectstack-ai/objectstack/blob/main/packages/plugins/driver-mongodb/README.md)
 
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