Revert "feat(ecc): prune plugin 43→12 items, promote 7 rules to .claude/rules/ (#245)"

This reverts commit 1bd68ff534.

.cursor/rules/golang-testing.md

@@ -0,0 +1,31 @@
+---
+description: "Go testing: table-driven tests, race detection, coverage reporting"
+globs: ["**/*.go"]
+alwaysApply: false
+---
+
+# Go Testing
+
+> This file extends [common/testing.md](../common/testing.md) with Go specific content.
+
+## Framework
+
+Use the standard `go test` with **table-driven tests**.
+
+## Race Detection
+
+Always run with the `-race` flag:
+
+```bash
+go test -race ./...
+```
+
+## Coverage
+
+```bash
+go test -cover ./...
+```
+
+## Reference
+
+See skill: `golang-testing` for detailed Go testing patterns and helpers.