docs: fix install URLs from mizchi/bit-vcs to bit-vcs/bit

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mizchi

docs/quick-start-ja.md

@@ -25,7 +25,7 @@ bit-relay は `bit hub` のメタデータ（Issue, PR, Note 等）を中継す
 
 ```bash
 # bit のインストール
-curl -fsSL https://raw.githubusercontent.com/mizchi/bit-vcs/main/install.sh | bash
+curl -fsSL https://raw.githubusercontent.com/bit-vcs/bit/main/install.sh | bash
 
 # relay の疎通確認
 curl https://bit-relay.mizchi.workers.dev/health

docs/usage-guide-ja.md

@@ -7,10 +7,10 @@ bit-relay を使ったリポジトリ共有・issue 管理・コラボレーシ
 
 ```bash
 # シェルスクリプト（Mac/Linux）
-curl -fsSL https://raw.githubusercontent.com/mizchi/bit-vcs/main/install.sh | bash
+curl -fsSL https://raw.githubusercontent.com/bit-vcs/bit/main/install.sh | bash
 
 # MoonBit パッケージマネージャ
-moon install mizchi/bit/cmd/bit
+moon install bit-vcs/bit/cmd/bit
 ```
 
 ```bash

docs/usage-guide.md

@@ -7,10 +7,10 @@ familiarity with Git.
 
 ```bash
 # Shell script (Mac/Linux)
-curl -fsSL https://raw.githubusercontent.com/mizchi/bit-vcs/main/install.sh | bash
+curl -fsSL https://raw.githubusercontent.com/bit-vcs/bit/main/install.sh | bash
 
 # MoonBit package manager
-moon install mizchi/bit/cmd/bit
+moon install bit-vcs/bit/cmd/bit
 ```
 
 ```bash