Summary

• Improve --verbose output to report step-by-step progress with actionable details:
  • output directory
  • jobs mode (auto/manual)
  • per-input JSON/XCResult test summaries
  • merged suite/test/attachment counts
  • per-format exported artifact path
• Change default job selection when --jobs is omitted to use 50% of available processors (max(1, cores/2)).
• Update CLI help text to document the new default jobs policy.
• Add tests for default automatic jobs and parse behavior for auto vs manual jobs mode.

Checklist

• I ran swift test
• I updated docs if behavior changed
• I added/updated tests for new behavior
• I verified CI-related files if workflow behavior changed

Validation

• Commands run:
  • swift test --filter defaultAutomaticJobsUsesHalfProcessorCount
  • swift test --filter parseJobsModeDefaultsToAutoAndSupportsOverride
  • swift test --filter verboseFlagAndDiagnosticLogs
  • swift test
  • .build/arm64-apple-macosx/release/snapshot-report --xcresult .artifacts/xcresult/UIKitSnapshots-generated-20260220-191759.xcresult --output /tmp/sr-verbose-validation --name "Verbose Validation" --format html --verbose

Screenshots / Artifacts (if applicable)

• N/A