fix: replace corepack with explicit pnpm version install from package.json

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Co-authored-by: TechWatching <15186176+TechWatching@users.noreply.github.com>

Author: Copilot

.github/workflows/template-sync.md

@@ -148,7 +148,7 @@ unresolved problems in the PR description.
 First, ensure pnpm is available and dependencies are installed:
 
 ```bash
-corepack enable 2>/dev/null || npm install -g pnpm
+npm install -g pnpm@$(node -p "require('./package.json').packageManager.split('@')[1]")
 pnpm install
 ```