Add Windsurf Cascade output

[chubes4]

Summary

• Adds a generated plugins/windsurf/ output for Windsurf/Cascade with Cascade-native .devin/rules/*.md files.
• Adds Windsurf MCP setup docs and mcp_config.json that reuse the existing WordPress.com / Jetpack MCP flow via wordpress-studio plus the shared telemetry server.
• Updates the build and verification scripts so the Windsurf output is generated and checked alongside Codex, Claude Code, Cursor, Continue, OpenCode, Roo Code, Gemini, and GitHub Copilot.

Official Windsurf/Cascade sources

• Rules and memories: https://docs.windsurf.com/windsurf/cascade/memories
• MCP configuration: https://docs.windsurf.com/windsurf/cascade/mcp
• AGENTS.md discovery: https://docs.devin.ai/desktop/cascade/agents-md
• Installation and onboarding: https://docs.windsurf.com/windsurf/getting-started

Tracking context

• Related: Add a GitHub Copilot plugin output #5 is Copilot-specific; this PR is parallel Windsurf/Cascade work.
• Ignored per task: feat: improve theme-creator skill score from 54% to 90% #3.

Verification

• pnpm install --frozen-lockfile
• pnpm build
• pnpm verify

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Drafted the Windsurf/Cascade output, generator updates, setup docs, verification updates, and rebase resolution for Chris to review and test.