Prove report-path precedence and independent defaults

[MariusStorhaug]

Context and request

#78 verifies the established default layout and verifies both direct output-path inputs together. It does not directly prove output paths loaded from a Pester configuration file, direct-input precedence over configuration-file values, or the behavior when only one report path is overridden.

The action contract should demonstrate that each report path is resolved independently and that the precedence described to consumers remains stable.

Acceptance criteria

• Add an action test where a Pester configuration file supplies both report paths.
• Add an action test where direct inputs override different configuration-file paths.
• Add coverage where only TestResult_OutputPath is set and code coverage retains its established default.
• Add coverage where only CodeCoverage_OutputPath is set and test results retain their established default.
• Assert generated XML and JSON report locations and artifact-upload inputs.
• Keep the existing default-layout behavior unchanged.

Technical decisions

Keep this item test-focused unless a failing case exposes an implementation defect. Use consumer-visible action tests rather than only testing the internal hashtable merge.

Implementation plan

1. Add configuration fixtures with distinct report paths.
2. Add the four action scenarios described in the acceptance criteria.
3. Assert final files and action outputs directly.
4. Update the report-path documentation only if the tests reveal a contract difference.