feat!: corner tips are required

DESIGN.md

@@ -17,7 +17,7 @@ Every WinLab app is framed by four fixed corners, 24px in from the viewport. `ap
 - There is no theme toggle: the theme follows the system.
 - CD passes `BUILD_SHA`, `BUILD_TIME` and `BUILD_URL` to the image build (`NEXT_PUBLIC_BUILD_*`); without them the version reads `dev`.
 - A corner with nothing to show stays empty.
-- Every corner item can carry a tip that says what its label leaves out (where a link goes, what a page holds, who owns the site). A tip never repeats the label. Tips open at once, toward the page, lined up with the corner's outer edge; touch never opens them, so nothing depends on one.
+- Every corner item has a tip (`tip` is required in `app-shell`, so a missing one fails the type check) that says what its label leaves out (where a link goes, what a page holds, who owns the site). A tip never repeats the label. Tips open at once, toward the page, lined up with the corner's outer edge; touch never opens them, so nothing depends on one.
 - Corner text is `text-body` in `muted-foreground`, links turn `foreground` on hover and when current.
 - Content that scrolls under the corners fades into a 64px band of frosted glass at the top and bottom edges.
 - No menu button: an app keeps its pages few enough to fit beside the breadcrumb on a phone.

app/[slug]/page.tsx

@@ -35,7 +35,11 @@ export default async function DocPage({
 
   return (
     <SiteShell
-      page={{ label: doc.title, href: `/${doc.slug}` }}
+      page={{
+        label: doc.title,
+        href: `/${doc.slug}`,
+        tip: doc.item ? `@winlab/${doc.item}` : doc.description,
+      }}
       layout={doc.layout ?? "spotlight"}
     >
       <div className="flex w-full flex-col items-center gap-12">

app/_docs/site-shell.tsx

@@ -6,7 +6,7 @@ export function SiteShell({
   layout,
   children,
 }: {
-  page?: { label: string; href: string }
+  page?: { label: string; href: string; tip: string }
   layout?: "column" | "spotlight" | "wide"
   children: React.ReactNode
 }) {

registry/winlab/blocks/app-shell/app-shell.tsx

@@ -12,10 +12,11 @@ import {
   TooltipTrigger,
 } from "@/registry/winlab/ui/tooltip"
 
-// A tip says what the label leaves out (where a link goes, what a page
-// holds); it never repeats the label.
-type Crumb = { label: string; href: string; tip?: string }
-type NavItem = { label: string; href: string; tip?: string }
+// Every corner item has a tip, required so none is forgotten. It says what
+// the label leaves out (where a link goes, what a page holds, whose account
+// it is); it never repeats the label.
+type Crumb = { label: string; href: string; tip: string }
+type NavItem = { label: string; href: string; tip: string }
 
 // The chrome of every WinLab app is its four corners. By default each corner
 // has one job, filled from the props below; an app that needs something else