Issue
JUNIT pattern is stored in env (publisher.collect_junit) and later consumed by datadog upload via shell env. This creates an implicit cross-library contract and hidden coupling.

Steps to reproduce
1. Review publisher.collect_junit() and triggerDatadogUploadIfEligible().
2. Observe env.JUNIT_PATTERN is set and used to populate JUNIT_FILTER build param.
3. Review datadog.uploadTestResults() and note export JUNIT_PATTERN and usage in shell.

Expected result
JUnit pattern is passed through an explicit, structured job context or parameter model.

Actual result
Global env mutation and shell env export are used as implicit API between components.

Plan

• Extend job execution context (CNV-78434 direction) to include junitPattern.
• Pass junitPattern through context JSON or explicit build param, not env.
• Update datadog uploader to read from context object or a single context JSON artifact.
• Remove env.JUNIT_PATTERN usage and related shell export.