WarpEngine Client: the whole catalog, and a build that can point elsewhere

**The app is called WarpEngine Client.** "Store" named the thing it opens rather than the
thing you run, and the store is a catalog on a site, not a window on your machine. The
window title, the bundle, the packages and the menu entry follow; the repository already
did. The store being driven is named in the side menu, so the bar stopped repeating it as
a badge — the element stays in the page, hidden, because the window check reads it.

**Every title is listed, including the ones this machine cannot install.** They arrive
from the engine with `installable: false` and a reason, and they are drawn dimmed, with an
*unsupported platform* or *no build for this machine* badge, the engine's own sentence
underneath, and nothing to press: a disabled Install would invite a click that can never
work. They get a category of their own — *Not for this machine* — and they are kept out of
the native/hosted categories and counts, because a title with no build has no mode to be
counted under. An engine older than desktop 1.2.0 is unaffected: a missing `installable`
field reads as installable, which is what those engines mean.

**A build can be pointed at another site's registry:**

    make dist STORES_API=https://games.example.org/api/stores

BuildConfiguration reads the packaged package.json, where electron-builder's
extraMetadata writes that address, so a client for somebody else's catalog needs no source
change and nothing set on the user's machine. Precedence is runtime environment, then
build, then ours — three audiences, most specific first.

Also: the scrollbars are the window's own, because the platform's light track down the
side menu of a dark window looked like a mistake.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

STRUCTURE.md

@@ -62,6 +62,7 @@ src/
     mappers/                  engine JSON → domain
     http/                     HttpTextClient, HttpStatusError
     json/                     JsonRecord: reading data that came from elsewhere
+    config/                   BuildConfiguration: what was decided when this was packaged
     electron/                 ApplicationEnvironment and GameLauncher adapters
   main/
     main.ts                   the entry point: one line of work
@@ -184,6 +185,14 @@ never calls the bridge.
 type, so a typo is a compile error and adding an entry is the whole change. This is
 the extension point for a second engine.
 
+### Build-time configuration
+
+`infrastructure/config/BuildConfiguration.ts` reads the packaged `package.json`, which is
+where a build records the registry it was made for (`warpEngine.registryUrl`, set by
+`make dist STORES_API=…`). Precedence is runtime environment, then build, then the
+built-in default — most specific first, and each one is a different audience: someone
+trying it out, someone shipping a client for another site, us.
+
 ### Untrusted-data readers
 
 Anything parsed from outside — engine stdout, the registry — goes through