Add a keyless Parallel Search MCP configuration and registry example

[georgeatparallel]

Adds an opt-in configuration for free, keyless Parallel Search MCP using the existing Streamable HTTP client. Merge the supplied server entry into mcp-servers.json to enable web search and page fetching. Existing server entries and model settings stay unchanged. A runnable Rust example loads that configuration and calls both tools through ToolRegistry without an LLM or saved OAuth credentials.

I work at Parallel. For context, here are Artificial Analysis’s Search API benchmarks.

Tested: anonymous live search and fetch through the registry, plus HTTP request capture for discovery, tool dispatch, User-Agent, and the absence of Authorization.

[stippi]

Thanks. I appreciate the openness, but don't want to merge as is. Main reasons are that the agent would get two overlapping web_fetch and web_search tools, and the MCP server could be configured today, without any changes. So this PR doesn't address any problem in the product or add a new feature. It mainly adds advertising for Parallel.