style: fix trailing whitespace in validation workflow and expand OTEL docs

- Remove trailing whitespace from validate-action-output.yml workflow file
- Add clarification to README about OpenTelemetry environment variable support
- Document that OTEL_ variables are automatically read from job steps
- Reference OpenTelemetry SDK environment variable specification for extended configuration options
- Improve documentation clarity for users configuring the action

Author: paper2

.github/workflows/validate-action-output.yml

@@ -151,7 +151,7 @@ jobs:
       - name: Generate normalized files
         run: |
           set -euo pipefail
-          
+
           jq -f /tmp/normalize-traces.jq collector-logs/traces-exported-original.json > collector-logs/traces-actual.json
           jq -f /tmp/normalize-metrics.jq collector-logs/metrics-exported-original.json > collector-logs/metrics-actual.json
 
@@ -193,15 +193,15 @@ jobs:
 
           ACTUAL_JOB_COUNT=$(jq -r '[.resourceSpans[]?.scopeSpans[]?.spans[]? | select(.name | startswith("job:"))] | length' collector-logs/traces-actual.json)
           EXPECTED_JOB_COUNT=${{ inputs.expected-job-count }}
-          
+
           echo "Expected job count: $EXPECTED_JOB_COUNT"
           echo "Actual job count: $ACTUAL_JOB_COUNT"
-          
+
           if [ "$ACTUAL_JOB_COUNT" -ne "$EXPECTED_JOB_COUNT" ]; then
             echo "✗ Job count mismatch: expected $EXPECTED_JOB_COUNT, got $ACTUAL_JOB_COUNT"
             exit 1
           fi
-          
+
           echo "✓ Job count validation passed"
 
       # Show final collector status and logs for debugging

README.md

@@ -217,6 +217,12 @@ To configure the action, you need to set the following environment variables:
 | `FEATURE_METRICS`                     | No       | `true`        | Enable Metrics feature.                                                                            |
 | `OTEL_LOG_LEVEL`                      | No       | `info`        | Log level.                                                                                         |
 
+This action relies on the OpenTelemetry SDK, which automatically reads `OTEL_`
+environment variables from `jobs.<job_id>.steps[*].env`. The table above lists
+commonly used variables, but other variables defined in the
+[OpenTelemetry Environment Variable Specification](https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/)
+may also work depending on SDK support.
+
 ### Getting Started
 
 We prepared a [Getting Started](./examples/google-cloud/README.md) to create