fix: include final memory release in optimization duration

[MataM15]

Summary

Include the final application memory-release stage in the reported optimization duration. This independent contribution is based on upstream main; candidate commit: 2d02579.

Related Issue

No exact issue identified.

Changes

• Measure total elapsed time through the final App.ReleaseMemory stage, including error paths.
• Use consistent elapsed-time reporting for existing success and failure reports without creating a successful optimization report when all native operations fail.
• Preserve the production garbage-collection sequence and working-set trimming behavior.
• Add ten focused tests for release sequencing, stage failures, and timing boundaries.

Checklist

• My code follows the project’s coding style and conventions.
• I have tested the changes locally.
• I have updated documentation if necessary. No new user setting is introduced.
• This PR does not introduce any breaking changes.
• I have added unit tests if applicable.

Additional Notes

Standalone hosted Windows validation: Release build with 0 warnings and 0 errors; all 10 selected NUnit tests passed on this exact candidate. This is focused validation, not a full-suite or performance-improvement claim.

GC is retained; no benchmark, fork-only workflow, or packaging tools are included. The release helper may need integration if the separate logging changes in #203 land first. Scope: 5 files, 366 changed lines.