docs: remove redundant CI_TESTING.md in favor of socket-registry docs

CI testing documentation is maintained centrally in socket-registry/CLAUDE.md.
No other socket- project duplicates this locally.

Author: jdalton

CI_TESTING.md

@@ -110,7 +110,7 @@ With `exactOptionalPropertyTypes`, assign conditionally:
 ### CI Testing
 - **🚨 MANDATORY**: `SocketDev/socket-registry/.github/workflows/ci.yml@<SHA>` with full SHA
 - **Format**: `@662bbcab1b7533e24ba8e3446cffd8a7e5f7617e # main`
-- **Docs**: `docs/CI_TESTING.md`, `socket-registry/docs/CI_TESTING_TOOLS.md`
+- **Docs**: `socket-registry/CLAUDE.md`, `socket-registry/docs/CI_TESTING_TOOLS.md`
 
 ### Debugging
 - Use benchmarks to verify parsing speed