Feature Request: Please Add native Toolport.app MCP gateway integration to Goose harness

**Motivation**

Goose (the default agent harness in Buzz) currently has no built-in support for Toolport, the open-source local MCP gateway that lets multiple AI clients share one set of MCP servers with up to 91% fewer tokens via lazy tool discovery [Toolport docs](https://toolport.app/). Users who run self-hosted Buzz + Goose alongside Toolport must manually configure each Goose agent to point at Toolport's gateway endpoint instead of individual MCP servers. This is repetitive, error-prone, and blocks the token-efficiency benefits that Toolport provides to other clients like Claude Code, Cursor, and GitHub Copilot CLI [Toolport GitHub Copilot docs](https://toolport.app/clients/github-copilot-cli/).

**Proposed solution**

Add native Toolport integration to the Goose harness in Buzz, similar to how Buzz already supports direct MCP server configuration. Specifically:

In the Agent Defaults / Harness configuration UI, add a "Toolport gateway" option alongside existing MCP server configuration.

When enabled, Goose agents automatically connect to Toolport's local gateway (default: http://127.0.0.1:) and use Toolport's 4 meta-tools (search_tools, call_tool, etc.) for on-demand tool discovery instead of loading all tool schemas into context upfront.

Support both stdio and HTTP transport modes for Toolport, matching Toolport's existing client integrations [Toolport Jan client docs](https://toolport.app/clients/jan/).

Persist the Toolport gateway URL and auth settings in the agent's harness config, so they survive agent restarts and session rotations.

This would let Buzz + Goose users benefit from Toolport's token reduction (74–91% fewer tokens at equal task success) without manual per-agent configuration [Reddit r/mcp](https://www.reddit.com/r/mcp/comments/1ulun87/13_mcp_servers_put_392_tool_definitions_in_my/).

**Alternatives considered**

Manual configuration per agent — Users can currently add Toolport as an MCP server in each Goose agent's config, but this duplicates effort across agents and doesn't scale to multi-agent teams.

Environment variable injection — Buzz could inject TOOLPORT_URL and TOOLPORT_API_KEY into the Goose process environment, but this bypasses the UI and requires users to know Toolport's internal config format.

**Additional context**

Toolport is already integrated with Claude Code, Cursor, VS Code Copilot, Jan, and 34+ other clients [Toolport clients page](https://toolport.app/clients/).

Buzz already supports MCP server configuration for agents; this would extend that to support MCP gateways like Toolport.

Related to existing Goose harness issues where Buzz injects incorrect environment variables (e.g., GOOSE_PROVIDER=openai-compat instead of translating to Goose's vocabulary) [#4569](https://github.com/block/buzz/issues/4569), [#2749](https://github.com/block/buzz/issues/2749).

Token benchmarks show MCP schema bloat is a major cost driver for multi-agent workspaces; Toolport's lazy discovery pattern directly addresses this [StackOne MCP vs CLI comparison](https://www.stackone.com/blog/mcp-vs-cli-for-ai-agents/).