Fix cache scope to use image name environment variables

- Change ESP-Matter cache scope from hardcoded 'esp-matter' to use ESP_MATTER_IMAGE_NAME
- Now both ESP-IDF and ESP-Matter use consistent pattern: ${env.<IMAGE_NAME>}-${platform}
- Update cursor rules to document cache scoping pattern
- Ensures cache scopes automatically update when image names change

Author: hacker-cb

.cursor/rules/github-actions-standards.mdc

@@ -178,6 +178,7 @@ jobs:
 - **Job naming**: Use `<image-name>-build` and `<image-name>-manifest` pattern (e.g., `esp-idf-build`, `esp-idf-manifest`)
 - **Benefits of image-first naming**: Jobs for same image group together in GitHub UI when sorted alphabetically
 - **Image name variables**: Use descriptive uppercase names like `ESP_IDF_IMAGE_NAME`, not generic `IMAGE_NAME`
+- **Cache scoping**: Use image name variable for cache scope: `scope=${{ env.<IMAGE_NAME> }}-${{ steps.platform.outputs.tag }}`
 - Matrix builds both platforms in parallel for faster CI
 - Platform-specific images tagged with arch suffix (e.g., `pio-6.1.18-linux-amd64`)
 - Manifest job combines platform images into multi-arch manifest

.github/workflows/esp-idf.yml

@@ -144,8 +144,8 @@ jobs:
           push: ${{ github.ref_name == 'master' }}
           tags: |
             ${{ env.REGISTRY }}/${{ github.repository_owner }}/${{ env.ESP_MATTER_IMAGE_NAME }}:idf-${{ matrix.jethome_idf_base_tag }}-matter-${{ matrix.esp_matter_version }}-${{ steps.platform.outputs.tag }}
-          cache-from: type=gha,scope=esp-matter-${{ steps.platform.outputs.tag }}
-          cache-to: type=gha,mode=max,scope=esp-matter-${{ steps.platform.outputs.tag }}
+          cache-from: type=gha,scope=${{ env.ESP_MATTER_IMAGE_NAME }}-${{ steps.platform.outputs.tag }}
+          cache-to: type=gha,mode=max,scope=${{ env.ESP_MATTER_IMAGE_NAME }}-${{ steps.platform.outputs.tag }}
           build-args: |
             BASE_IMAGE_TAG=idf-${{ matrix.jethome_idf_base_tag }}-${{ steps.platform.outputs.tag }}
             ESP_MATTER_VERSION=${{ matrix.esp_matter_version }}