describe-changes@v1: with concatenate mode: append

✨ PR Description

Purpose: Fix daily test matrix functionality to support Hello Elementor theme naming and improve CI workflow reliability.
Main changes:

• Updated CSS tests to detect files from both hello-theme and hello-elementor theme directories
• Modified theme build process to use consistent hello-elementor naming across workflows
• Added fallback mechanisms and improved error handling for CI stability
• Improved npm installation resilience with multiple retry strategies

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