Fix the media process lifecycle and the critical validation outcome

[Kentarohakase]

Three fixes around the processing pipeline, plus the changelog entry that was missing for them.

Fixed

• A critical result validation reported success. ValidateAsync returned Result.Success for every report it managed to build, including one with AudioComparisonStatus.Critical. The affected file counted as exported successfully and only produced a warning line. It now fails the item, with the report still attached so the findings stay visible in the validation panel.
• A stopped run was misreported. The inactivity watchdog only set a flag; the wait for the process kept running until the user cancelled, and the result was then labelled a cancellation. A timeout now ends the wait directly through a linked token and is reported as a timeout, while only an actual cancellation is reported as one.
• Output was read while it was still being written. After a kill the app now waits briefly for the process to exit, stops the output readers, and reads the captured buffers under a lock. The watchdog also no longer tries to kill a process that has already exited.

Changed

• scripts/package-release.ps1 requires an explicit -Version in major.minor.patch form. The previous default was a stale 0.2.0, so a forgotten argument silently produced a mislabelled package. release.yml always passes the value explicitly and is unaffected.

Verification

dotnet format .\AudioQualityEnhancer.slnx --verify-no-changes   -> clean
dotnet build  .\AudioQualityEnhancer.slnx -c Release            -> 0 warnings, 0 errors
dotnet test   .\AudioQualityEnhancer.slnx -c Release            -> 195 passed, 0 failed

Release builds carry TreatWarningsAsErrors, so the build is the real gate here.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve the released 0.17.0 changelog section

Replacing the 0.17.0 heading with Unreleased removes that released version from the changelog and incorrectly groups its existing update-check and drag-and-drop entries with the new fixes. Add a separate Unreleased section above the original ## 0.17.0 - 2026-06-13 heading so the published release history remains accurate.

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