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>

src/shared/contracts/dto/GameDto.ts

@@ -1,6 +1,9 @@
 /** How a title runs: unpacked on this machine, or served as a web build. */
 export type GameModeDto = 'app' | 'web'
 
+/** Why a title cannot be installed on this machine. */
+export type UnavailableReasonDto = 'platformOff' | 'hostAsset' | 'noAsset' | 'vetoed'
+
 /**
  * A catalog entry as the window needs it.
  *
@@ -23,4 +26,8 @@ export interface GameDto {
   readonly updateAvailable: boolean
   readonly installedVersion: string | null
   readonly launchable: boolean
+  /** False for a title this machine cannot install; it is listed all the same. */
+  readonly installable: boolean
+  readonly unavailableReason: UnavailableReasonDto | null
+  readonly unavailableDetail: string | null
 }