Fix npm cache corruption in base blueprint

Add `npm cache clean --force` at the end of the base blueprint setup
to prevent "idealTree already exists" errors in child blueprints.

The npm global install leaves cache state that can cause issues when
child blueprints run their own npm install commands.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/runloop-blueprint-template.json

@@ -15,7 +15,8 @@
     "sudo chmod go+r /usr/share/keyrings/githubcli-archive-keyring.gpg",
     "echo 'deb [arch=amd64 signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main' | sudo tee /etc/apt/sources.list.d/github-cli.list > /dev/null",
     "sudo apt update",
-    "sudo apt install -y gh"
+    "sudo apt install -y gh",
+    "npm cache clean --force"
   ],
   "launch_parameters": {
     "launch_commands": [