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

ECC community plugin pruning: removed 530+ non-essential files
(.cursor/, .opencode/, docs/ja-JP, docs/zh-CN, docs/zh-TW,
language-specific skills/agents/rules). Retained 4 agents,
3 commands, 5 skills. Promoted 13 rule files (8 common + 5
typescript) to .claude/rules/ for CC native loading. Extracted
reusable patterns to EXTRACTED-PATTERNS.md.

rules/golang/patterns.md

@@ -1,45 +0,0 @@
----
-paths:
-  - "**/*.go"
-  - "**/go.mod"
-  - "**/go.sum"
----
-# Go Patterns
-
-> This file extends [common/patterns.md](../common/patterns.md) with Go specific content.
-
-## Functional Options
-
-```go
-type Option func(*Server)
-
-func WithPort(port int) Option {
-    return func(s *Server) { s.port = port }
-}
-
-func NewServer(opts ...Option) *Server {
-    s := &Server{port: 8080}
-    for _, opt := range opts {
-        opt(s)
-    }
-    return s
-}
-```
-
-## Small Interfaces
-
-Define interfaces where they are used, not where they are implemented.
-
-## Dependency Injection
-
-Use constructor functions to inject dependencies:
-
-```go
-func NewUserService(repo UserRepository, logger Logger) *UserService {
-    return &UserService{repo: repo, logger: logger}
-}
-```
-
-## Reference
-
-See skill: `golang-patterns` for comprehensive Go patterns including concurrency, error handling, and package organization.