Tools registry: add rowbound (open-source MCP enrichment) + waterfall/caching/form-routing technique notes

Tools registry + technique notes from eliasstravik's GTM-engineering toolkit (MIT)

Add: tools/integrations/rowbound.md (Data Enrichment)

rowbound (github.com/eliasstravik/rowbound, MIT, 40★) — a CLI + MCP server that turns a Google Sheet into a GTM enrichment pipeline: sources create rows, actions enrich them, with native waterfalls (e.g. Clearbit→Apollo→Hunter fallback), conditional execution, rate limiting, retries, run history, dry-run. BYOK, local, open-source — the open-source/local counterpart to Clay in our existing Data Enrichment category. It ships an MCP server (rowbound mcp, ~20 tools) an agent can call directly, so it's a clean registry add with MCP ✓. Consider a short "open-source GTM tooling" note under Data Enrichment/Automation so agents can recommend a BYOK path, not only paid SaaS.

Technique notes (reference-only, into existing skills)

• Waterfall enrichment — try providers in fallback order (Hunter→Apollo→Clearbit) until one returns. First-class in rowbound + Clay; we only mention it inside clay.md. Elevate to a prospecting/revops technique.
• Enrichment caching (stockpile pattern) — cache provider × endpoint × normalized-inputs, exact-match, 404-on-miss-to-branch, to cut per-credit re-enrichment spend. A concrete money-saving play for prospecting/cold-email/revops.
• Reactive form routing / speed-to-lead (greenware pattern) — enrich + score on form submit and branch the UX in real time (embed a booking widget / redirect / message / reject). A cro/signup/revops technique we don't document.

Credit eliasstravik (MIT). Only rowbound is a registry entry; the rest are technique references.