Desktop app: one interface, two hosts — plus in-process ONNX and document extraction

[peopleworks]

A Reddit user asked for a desktop version. This is it, plus the two libraries that will make it
worth downloading.

What changed

The interface moved out of the web project. Every page, component and UI service now lives in
SignsOfAI.UI, a Razor class library. SignsOfAI.Web keeps only what a host owns — index.html,
the icons, the deployment config, the WASM bootstrap — and the new SignsOfAI.Desktop (WPF +
WebView2) renders the very same components in a window. A change to the interface lands in both at
once; there is no second copy to keep in step.

SignsOfAI.Onnx extracts the perplexity and embedding engines out of the HTTP server into a
library, so a host can run them in-process instead of over the network. Moved, not rewritten.

SignsOfAI.Documents reads PDF, DOCX, ODT, EPUB, RTF, TXT and Markdown, with page/paragraph
structure so a finding maps back to somewhere the reader can look.

Two host differences that are handled, not papered over

• Static assets. A native HttpClient cannot reach a WebView's virtual host, so the i18n loader
  reads through a JS fetch helper. One code path for both hosts rather than an abstraction with two
  implementations — and it removed the HttpClient bound to HostEnvironment.BaseAddress entirely.
• Startup order. The web app resolves the language before the first render; the desktop cannot,
  because JS interop only wakes once the WebView has booted. Loc.EnsureInitializedAsync is
  idempotent and App.razor holds the router back until it completes, so neither host renders
  half-translated.

Two things reviewers should know

SignsOfAI.Desktop is deliberately not in SignsOfAI.slnx. It is WPF, and three workflows build
that solution on ubuntu-latest. It lives in SignsOfAI.Desktop.slnx with its own windows-latest
job, which keeps the main build on Linux where it stays fast for translation pull requests. There is
a comment at the top of the solution file saying so, because Visual Studio will offer to add it.
nuget.yml now names its solution explicitly: a second .slnx makes a bare dotnet test stop with
MSB1011.

The desktop TFM pins a Windows platform version on purpose. BlazorWebView hosts the page in
WebView2's composition control, which reaches for the Windows SDK WinRT projections. Without the
pin the app builds clean and dies at the first render.

Verification

• 204 tests pass (125 Core + 72 Documents + 7 ONNX). Both new test projects were previously outside
  any integrated build — that is how a test assertion ending in || true survived; it is fixed and
  now asserts the real behaviour.
• Both solutions build in Release with no warnings.
• The web app is unchanged: every asset resolves, the EN/ES switch works, and the English sample
  still scores 94/100 with 23 recommendations.
• The perplexity API still answers after the extraction, with real inference through the new
  library — ppl 27.33, predictability 0.859, very-predictable, 411ms.
• The desktop app launches and renders the shared interface.

What CI is being asked here that a Windows machine could not answer: the two new projects have
never been built on Linux. The ONNX test project conditions its RID and native package on
IsOSPlatform('Windows') and its model-dependent tests return early when the weights are absent
(they are git-ignored, so CI has none). That reasoning looks right, but only this run proves it.

Not in this PR

The desktop still does nothing a browser tab cannot. Wiring SignsOfAI.Onnx into it (offline
perplexity, no server, nothing uploaded), SignsOfAI.Documents (drop a folder), and local Ollama —
a CORS wall from a page, an ordinary HTTP call from here — is the next step.

🤖 Generated with Claude Code