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

This reverts commit 1bd68ff534.

rules/golang/security.md

@@ -0,0 +1,34 @@
+---
+paths:
+  - "**/*.go"
+  - "**/go.mod"
+  - "**/go.sum"
+---
+# Go Security
+
+> This file extends [common/security.md](../common/security.md) with Go specific content.
+
+## Secret Management
+
+```go
+apiKey := os.Getenv("OPENAI_API_KEY")
+if apiKey == "" {
+    log.Fatal("OPENAI_API_KEY not configured")
+}
+```
+
+## Security Scanning
+
+- Use **gosec** for static security analysis:
+  ```bash
+  gosec ./...
+  ```
+
+## Context & Timeouts
+
+Always use `context.Context` for timeout control:
+
+```go
+ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+defer cancel()
+```