tweak

tests/test_build_components/common/README.md

@@ -192,38 +192,9 @@ Components tested individually when they:
 
 ### Making Components Groupable
 
-Some components originally used `!extend` directives to add platform-specific parameters. These have been refactored to inline the full configuration, making them groupable:
+**WARNING**: Using `!extend` or `!remove` directives in component test files prevents automatic component grouping in CI, making builds slower.
 
-**Before (non-groupable)**:
-```yaml
-# test.esp32-s3-idf.yaml
-packages:
-  common: !include common.yaml
-
-light:
-  - id: !extend led_strip1
-    use_dma: "true"  # ESP32-S3 specific parameter
-```
-
-**After (groupable)**:
-```yaml
-# test.esp32-s3-idf.yaml
-# Configuration is inlined instead of using !extend to make this component groupable.
-# Using !extend prevents automatic component grouping in CI, requiring individual builds.
-light:
-  - platform: esp32_rmt_led_strip
-    id: led_strip1
-    pin: ${pin1}
-    num_leds: 60
-    rgb_order: GRB
-    chipset: ws2812
-    use_dma: "true"  # ESP32-S3 specific parameter inlined
-```
-
-**Migrated components**:
-- `remote_receiver/test.esp32-s3-idf.yaml` - Inlined DMA configuration
-- `remote_transmitter/test.esp32-s3-idf.yaml` - Inlined DMA configuration
-- `esp32_rmt_led_strip/test.esp32-s3-idf.yaml` - Inlined DMA configuration for two LED strips
+When platform-specific parameters are needed, inline the full configuration rather than using `!extend` or `!remove`. This allows the component to be grouped with other compatible components, reducing CI build time.
 
 **Note**: Some components legitimately require `!extend` or `!remove` for platform-specific features (e.g., `adc` removing ESP32-only `attenuation` parameter on ESP8266). These are correctly identified as non-groupable.