chore(devcontainer): align pnpm version with the ci

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: KSXGitHub

.devcontainer/full/post-create.sh

@@ -5,7 +5,7 @@ echo "Installing Python dependencies..." >&2
 python3 -m pip install --user toml
 
 echo "Installing pnpm and project Node dependencies..." >&2
-npm install -g pnpm@7.33.7
+npm install -g pnpm@7.9.0
 (cd ci/github-actions && pnpm install --frozen-lockfile)
 
 bash "$(dirname "$0")/../install-hyperfine.sh"