Use the abs filter instead of an abs() call in the stove and HVAC blueprints

Home Assistant's template engine has no abs() function, so every run of
Stove On Detection failed at its first variable ("'abs' is undefined") and
the HVAC failure monitor would fail the same way. Deployment note now points
at labctl blueprints:pull ha.

Claude-Session: https://claude.ai/code/session_01JBPyi1vyBbme5DKykW3Z25

CLAUDE.md

@@ -10,9 +10,9 @@ This is a Home Assistant Blueprints repository containing reusable automation te
 ### Deployment
 After committing and pushing changes, deploy blueprints to Home Assistant:
 ```bash
-HA_POD=$(kubectl -n ha get pods -l app=ha-app -o=jsonpath="{.items[0].metadata.name}")
-kubectl -n ha exec "$HA_POD" -- bash -c "cd /config/blueprints/automation/rzen && git pull"
+labctl blueprints:pull ha      # from the lab repo; runs git pull in the checkout on the ha volume
 ```
+Then reload automations in the Home Assistant UI (Developer tools → YAML → Automations) so blueprint changes take effect.
 
 ### Testing & Validation
 - **Blueprint Validation**: Use Home Assistant's built-in blueprint importer to validate YAML syntax