Migrate mcp-server/ from cadence-lang.org to onflow/flow-ai-tools

[Aliserag]

Per pr285-evaluation 2026-04-26-design.md follow-up.

PR #285 (the redesign + AI tools) ships the MCP server inline at mcp-server/ because it was tightly coupled to content/docs/ for search indexing. Long-term home should be the official Flow plugin marketplace at onflow/flow-ai-tools, so all Flow-related Claude Code skills + MCP servers version + release together.

Scope

• Move mcp-server/ to onflow/flow-ai-tools/mcp-servers/cadence-mcp/ (or wherever fits the marketplace structure)
• Update build/test workflows
• Keep npm package name @outblock/cadence-mcp for now (separate rename issue tracks that)
• The doc-search index can be regenerated from the docs site's published /llms.txt + /llms-full.txt rather than reading source MDX directly — decouples release cycles
• Update install-snippet references in content/docs/ai-tools/{mcp-server,integrations/*}.mdx after the move (they currently say npx -y @outblock/cadence-mcp which would still work)

Non-goals

• Functionality changes
• API / protocol changes

[Aliserag]

Superseded by #306's MCP consolidation — mcp-server/ was removed from the redesign PR entirely. The canonical Cadence MCP is now flow mcp (Flow CLI built-in, onflow/flow-cli#2306). The 3 unique tools that lived in mcp-server/ (security scan, JSON-CDC validation, doc search) are tracked for upstream port at #307.