fix(githooks): use absolute-git-dir to find worktree in post-receive

`git rev-parse --show-toplevel` in hook context (cwd=GIT_DIR, GIT_DIR
set) returns the .git path itself without erroring, so the previous
`|| echo $PWD` fallback never triggered and the script silently
cd'd into .git/.

Use `git rev-parse --absolute-git-dir` to reliably get the absolute
git-dir, then its parent is the worktree root. This works in both
interactive shells and hook context.

.githooks/post-receive

@@ -7,8 +7,17 @@ export NVM_DIR="$HOME/.nvm"
 [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm
 [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"  # This loads nvm bash_completion
 
-REPO_TOPLEVEL="$(git rev-parse --show-toplevel 2>/dev/null || echo "$PWD")"
+# git 调钩子时 cwd=GIT_DIR。此时 `git rev-parse --show-toplevel` 返回
+# `/.../repo/.git`（不报错，所以原版的 `|| echo $PWD` 退路不会触发），
+# 会让 cd 误进 .git 目录。安全办法：拿绝对 git-dir 路径，取其父目录。
+GIT_DIR_ABS="$(git rev-parse --absolute-git-dir 2>/dev/null)"
+if [ -n "$GIT_DIR_ABS" ] && [ -d "$GIT_DIR_ABS" ]; then
+    REPO_TOPLEVEL="$(cd "$GIT_DIR_ABS/.." && pwd)"
+else
+    REPO_TOPLEVEL="$(git rev-parse --show-toplevel 2>/dev/null || echo "$PWD")"
+fi
 cd "$REPO_TOPLEVEL" || { echo "FATAL: cannot cd to $REPO_TOPLEVEL" >&2; exit 1; }
+echo "=== REPO_TOPLEVEL=$REPO_TOPLEVEL (GIT_DIR_ABS=$GIT_DIR_ABS) ===" >&2
 
 # ============================================================
 # 0. sync_worktree —— 将工作树同步到新 push 的 HEAD