docs: fix cp -r flatten install instructions that silently overwrite rules

The configure-ecc skill (English source) and ja-JP top-level README plus
its configure-ecc translation documented `cp -r .../<lang>/* <target>/rules/`
for installing rule directories. rules/README.md explicitly warns against
this form because:

- Common and language-specific directories contain same-named files
  (coding-style.md, testing.md, patterns.md, hooks.md, security.md).
  Flattening makes each language overwrite the previous and common.
- The relative `../common/<file>.md` references in language rule files
  break when common/ is no longer a sibling directory.

This is silent — the user gets only the last language's rules with no
error message.

Replace with the directory-form copy already documented in
rules/README.md:

    cp -r .../<lang> <target>/rules/<lang>

Scope: English source + ja-JP. Closes #1879. Other locale translations
(zh-CN, ko-KR, pt-BR, tr) carry the same pattern and can follow up as
separate PRs to keep this change reviewable.

docs/ja-JP/README.md

@@ -122,12 +122,12 @@
 git clone https://github.com/affaan-m/everything-claude-code.git
 
 # 共通ルールをインストール（必須）
-cp -r everything-claude-code/rules/common/* ~/.claude/rules/
+cp -r everything-claude-code/rules/common ~/.claude/rules/common
 
 # 言語固有ルールをインストール（スタックを選択）
-cp -r everything-claude-code/rules/typescript/* ~/.claude/rules/
-cp -r everything-claude-code/rules/python/* ~/.claude/rules/
-cp -r everything-claude-code/rules/golang/* ~/.claude/rules/
+cp -r everything-claude-code/rules/typescript ~/.claude/rules/typescript
+cp -r everything-claude-code/rules/python ~/.claude/rules/python
+cp -r everything-claude-code/rules/golang ~/.claude/rules/golang
 ```
 
 ### ステップ3：使用開始
@@ -462,15 +462,15 @@ Duplicate hook file detected: ./hooks/hooks.json is already resolved to a loaded
 >
 > # オプション A：ユーザーレベルルール（すべてのプロジェクトに適用）
 > mkdir -p ~/.claude/rules
-> cp -r everything-claude-code/rules/common/* ~/.claude/rules/
-> cp -r everything-claude-code/rules/typescript/* ~/.claude/rules/   # スタックを選択
-> cp -r everything-claude-code/rules/python/* ~/.claude/rules/
-> cp -r everything-claude-code/rules/golang/* ~/.claude/rules/
+> cp -r everything-claude-code/rules/common ~/.claude/rules/common
+> cp -r everything-claude-code/rules/typescript ~/.claude/rules/typescript   # スタックを選択
+> cp -r everything-claude-code/rules/python ~/.claude/rules/python
+> cp -r everything-claude-code/rules/golang ~/.claude/rules/golang
 >
 > # オプション B：プロジェクトレベルルール（現在のプロジェクトのみ）
 > mkdir -p .claude/rules
-> cp -r everything-claude-code/rules/common/* .claude/rules/
-> cp -r everything-claude-code/rules/typescript/* .claude/rules/     # スタックを選択
+> cp -r everything-claude-code/rules/common .claude/rules/common
+> cp -r everything-claude-code/rules/typescript .claude/rules/typescript     # スタックを選択
 > ```
 
 ---
@@ -487,10 +487,10 @@ git clone https://github.com/affaan-m/everything-claude-code.git
 cp everything-claude-code/agents/*.md ~/.claude/agents/
 
 # ルール（共通 + 言語固有）をコピー
-cp -r everything-claude-code/rules/common/* ~/.claude/rules/
-cp -r everything-claude-code/rules/typescript/* ~/.claude/rules/   # スタックを選択
-cp -r everything-claude-code/rules/python/* ~/.claude/rules/
-cp -r everything-claude-code/rules/golang/* ~/.claude/rules/
+cp -r everything-claude-code/rules/common ~/.claude/rules/common
+cp -r everything-claude-code/rules/typescript ~/.claude/rules/typescript   # スタックを選択
+cp -r everything-claude-code/rules/python ~/.claude/rules/python
+cp -r everything-claude-code/rules/golang ~/.claude/rules/golang
 
 # コマンドをコピー
 cp everything-claude-code/commands/*.md ~/.claude/commands/

docs/ja-JP/skills/configure-ecc/SKILL.md

@@ -169,13 +169,13 @@ Options:
 
 インストールを実行：
 ```bash
-# 共通ルール（rules/ にフラットコピー）
-cp -r $ECC_ROOT/rules/common/* $TARGET/rules/
+# 共通ルール
+cp -r $ECC_ROOT/rules/common $TARGET/rules/common
 
-# 言語固有のルール（rules/ にフラットコピー）
-cp -r $ECC_ROOT/rules/typescript/* $TARGET/rules/   # 選択された場合
-cp -r $ECC_ROOT/rules/python/* $TARGET/rules/        # 選択された場合
-cp -r $ECC_ROOT/rules/golang/* $TARGET/rules/        # 選択された場合
+# 言語固有のルール（言語別ディレクトリを保持）
+cp -r $ECC_ROOT/rules/typescript $TARGET/rules/typescript   # 選択された場合
+cp -r $ECC_ROOT/rules/python $TARGET/rules/python            # 選択された場合
+cp -r $ECC_ROOT/rules/golang $TARGET/rules/golang            # 選択された場合
 ```
 
 **重要**: ユーザーが言語固有のルールを選択したが、共通ルールを選択しなかった場合、警告します：