docs, tests: add Parallel Search MCP as optional web search setup (#1179)

[AyushDubey23]

Saw #1179 asking about an optional keyless web search setup via Parallel Search MCP, so put this together in case it's actually useful to anyone. No hard feelings if not needed or if you prefer a different direction.

What’s here

• Docs (docs/integrations/mcp.mdx): Added Parallel Search (https://search.parallel.ai/mcp) to the MCP integrations page as an example of a keyless remote web search server over HTTP (good for CVE/advisory research without setting up a Perplexity key).
• Tests (tests/test_mcp_client.py): Added unit tests covering config loading for keyless HTTP MCP servers as well as tool discovery and invocation.

Closes #1179 (or at least covers the setup example & test suite if you want to merge it).

[greptile-apps]

Greptile Summary

The PR documents Parallel Search as an optional keyless HTTP MCP integration and adds focused tests for its supported configuration and registry behavior.

• Adds a Parallel Search example to the MCP integrations guide.
• Verifies that keyless HTTP MCP configuration loads with optional notes.
• Verifies tool discovery and invocation through an adopted MCP session.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or non-blocking defects identified.

The documented configuration is accepted by the existing MCP schema and keyless HTTP client path, while the added tests correctly validate configuration parsing, discovery, and invocation behavior.

Important Files Changed

Filename	Overview
docs/integrations/mcp.mdx	Adds a valid keyless Parallel Search HTTP configuration consistent with the existing MCP configuration contract.
tests/test_mcp_client.py	Adds focused loader and registry-level tests without changing production behavior.

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