[codex] Add smart templates and reliability polish

[ZaidNAlAsali]

Summary: adds smart output filename template tokens, fixes an FFmpeg stdout pipe deadlock risk, reports non-zero FFmpeg exit codes, adds a repair command for Explorer shell registration, and adds a Windows MSBuild CI workflow. Why: keeps the existing Explorer-first workflow but improves reliability, repairability, and maintainability without a rewrite. Validation: git diff --check; XML parse checks for edited resx, wixproj, xaml, and sample preset files. Full local MSBuild was not available because this machine has no Visual Studio/MSBuild or .NET SDK installed.

[ZaidNAlAsali]

Added a third commit from a broader maintenance audit: c4cd4e0 fix: polish conversion maintenance edge cases. Highlights: graceful handling for no-extension inputs, malformed settings/presets, invalid cultures, missing shell-extension registry data, and failed URL/process launches; safer cleanup for Office COM conversions, CDA extraction, FFmpeg multi-pass intermediates, GIF/ICO/Office temp files, and Explorer temporary input-list files; fixed Excel page counting across worksheets, ImageMagick PDF page-count density usage, AVIF settings UI visibility, upgrade-check null awaits, and invalid CLI argument shutdown behavior. Validation repeated after the audit pass: git diff --check; XML/XAML/project parse validation for 21 files. Full local compilation still was not possible in this environment because no .NET SDK, NuGet, or Visual Studio/MSBuild is installed on PATH.