Serply search block for agent workflows

Feature request

Add Serply (https://serply.io) as a web search integration, alongside the existing Serper and Tavily blocks.

Serply is a Google SERP API with API-key auth. The integration would follow the established pattern exactly: a serply_search tool (GET https://api.serply.io/v1/search/, X-Api-Key header, organic results mapped to title/link/snippet) plus a Serply block with query, number of results, and API key fields. Fully optional, no new required env vars, no changes for anyone not using it.

I have this built and tested (tool + block + registrations + vitest coverage, ~226 lines across 5 files) and can open a PR against staging right away. Happy to be assigned this, and equally happy to adjust scope or drop it if another search provider is not a direction you want.

Disclosure: I work with Serply.

Label: feature