docs: sync action.yml description with README.md (#47)

Also add guidance to CLAUDE.md about keeping descriptions in sync.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: massongit

CLAUDE.md

@@ -19,6 +19,9 @@ This project maintains bilingual documentation:
 **Important**: When updating either readme file, the other must be updated accordingly.
 Keep both files synchronized with the same content in the appropriate language.
 
+**Important**: README.md's description (line 5) must match action.yml's `description` field.
+When updating one, update the other accordingly. Note that action.yml's description should not have a trailing period.
+
 ## Setup
 
 ### Install pre-commit (Recommended)

action.yml

@@ -1,6 +1,6 @@
 name: "actions-workflow-metrics"
 author: "Masaya Suzuki"
-description: "A custom GitHub Action that collects system metrics (CPU load, memory usage) during workflow execution and visualizes them as Mermaid charts"
+description: "A GitHub Actions for collecting system metrics during workflows and outputting Mermaid charts"
 inputs:
   interval_seconds:
     description: "Interval between metrics collection in seconds"