Add a Parallel Search MCP walkthrough

[georgeatparallel]

What this changes

Adds a focused Parallel Search MCP walkthrough, then links it from the two existing MCP server indexes. The guide covers the keyless remote setup, the two available tools, one practical prompt, verification, and troubleshooting.

Checklist (see CONTRIBUTING.md)

• Date-sensitive claims are anchored to a version or date (not applicable; no date-sensitive claims added)
• Renamed/removed headings keep a compatibility anchor (not applicable; no headings renamed or removed)
• New skills are tested and documented (not applicable; this adds an MCP walkthrough, not a skill)
• Tables are used for comparable content and the copy avoids marketing language

Validation

• confirmed the documented command shape against claude mcp add --help
• completed a live MCP initialize request and confirmed tools/list returns web_search and web_fetch
• checked all new local links and confirmed the official documentation returns HTTP 200
• git diff --check

Disclosure: I work at Parallel.ai, which operates this MCP endpoint.