[Regstar2]

Problem

During a real ISO E2E build the WPF build panel can remain visually unchanged for a long interval while the backend is still working. The stage text is still correct (Downloading Windows files… / Загрузка файлов Windows…), but when precise progress telemetry does not change the determinate bar also stops moving and the application looks frozen.

Closes #17 after merge to master.

Scope

UI-only liveness affordance.

• preserve the existing localized stage/status text;
• preserve the existing determinate Progress value and backend progress semantics;
• add a compact WPF ProgressBar with IsIndeterminate="True" beside the active status/speed row;
• the activity indicator exists only inside the ShowBuildProgress panel, so it is not active when the build panel is idle/completed/failed/cancelled;
• reuse the localized Status binding for accessibility instead of adding new hardcoded UI text;
• do not change Backend Contract v1, NDJSON events, build stages, cancellation, download logic, or progress calculation.

Microsoft WPF documents ProgressBar.IsIndeterminate as generic continuous feedback for work whose precise progress is not currently available. The existing determinate bar remains the source for known numeric progress.

Regression coverage

tests/BuildProgressLiveness.Tests.ps1 verifies that:

• the existing determinate progress binding remains present;
• the named liveness indicator is indeterminate;
• the indicator is contained in the active build panel;
• no new hardcoded liveness label is introduced.

Manual acceptance

Still required before merge:

1. build/run the GUI from this branch;
2. start a real ISO build;
3. wait for a quiet download/conversion interval where the numeric bar stops changing;
4. confirm the compact activity indicator continues animating and the Cancel button remains responsive;
5. check both RU and EN and light/dark themes for clipping/readability.

Dependency

This is intentionally a stacked Draft PR based on fix/v1.0.0-powershell51-form-post so the PowerShell 5.1 release-blocker fix remains a separate logical change. After PR #16 is accepted, retarget/rebase this PR to master before merging.

[Regstar2]

Validation note for audit trail:

• PR Keep build progress visibly active during quiet phases #18 was temporarily retargeted to master only to exercise the existing master-targeted self-hosted workflow.
• Run #188 executed the new BuildProgressLiveness.Tests.ps1; all 3 liveness regressions passed.
• Full validation then failed independently in GUI compilation with CS7065: Unable to read beyond the end of the stream while compiling the Win32 application resource. The synthetic merge included the newer master icon asset changes; this PR does not modify any icon asset.
• The PR has been retargeted back to fix/v1.0.0-powershell51-form-post to restore the intended two-file scope and preserve the hotfix dependency boundary.

Do not interpret run #188 as a failure of the liveness change. Full release validation and the manual RU/EN + light/dark real-build UI check remain required before merge.

[Regstar2]

Superseded by consolidated Draft PR #23. The build-liveness indicator and its regression coverage are included there together with the other E2E release blockers, per the request for one final PR. This PR is being closed without merge.