Fix Codecov unknown coverage and test analytics configuration

[RAprogramm]

Problem

Codecov shows 'unknown coverage' and test analytics are not properly separated from coverage reporting.

Root Cause

1. nextest.toml: Incorrect JUnit XML path causes double-nesting

   • Current: path = "target/nextest/ci/junit.xml"
   • Creates file at: target/nextest/ci/target/nextest/ci/junit.xml

2. reusable-ci.yml: OIDC authentication may not work without special permissions

   • Using use_oidc: true instead of token-based auth
   • Less reliable for protected branches

Solution

1. Fix nextest.toml: Use path = "junit.xml" (nextest auto-places in profile dir)
2. Replace OIDC with token: Use token: ${{ secrets.CODECOV_TOKEN }}
3. Enable auto-discovery for test results

Files to Change

• .config/nextest.toml
• .github/workflows/reusable-ci.yml