feat(ui): separate dev info into a Diagnose view, declutter the scan workspace

Reworks the UI so the Scan tab shows only core actions and all developer /
diagnostic surfaces live in one dedicated view.

- New "Diagnose" nav view. ScanView stays mounted for scan|diagnose (the scan
  controller state persists across the switch) and renders either the clean
  workspace or the new DiagnosticsView by mode.
- DiagnosticsView consolidates runtime/rights, grid detection, learning + data
  staleness, fingerprint, auto-scan counters, the automation log, the dev-output
  toggle, the Demo-Daten action, and the raw crops/OCR/confidence dump. Reuses
  the existing diagnostics/details model hooks.
- Scan workspace decluttered: removed the Scanner Diagnose button and the Details
  button, dropped the rules/grid/mode dev fields from the result brief and capture
  meta, shortened the topbar headline, and moved Demo-Daten out of the topbar.
- Removed the now-dead ScanDiagnosticsModal / ScanDetailsModal components (their
  content moved into the view); metrics grid hidden on the Diagnose view.
- Added dev:web script + .claude/launch.json for browser preview.

Verified in the browser preview (both views render, no console errors); 120
tests + build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/features/layout/AppLayout.tsx

@@ -90,7 +90,7 @@ export function AppTopbar({
     <header className="topbar">
       <div>
         <p className="eyebrow">Lokaler Windows-Assistent</p>
-        <h1>Scanne dein Inventar, triff einfache Artifact-Entscheidungen.</h1>
+        <h1>Inventar scannen, Artifacts entscheiden.</h1>
       </div>
       <div className="topbar-actions">
         {topbarStatus && <span className="topbar-status">{topbarStatus}</span>}
@@ -107,15 +107,6 @@ export function AppTopbar({
           {overlayIcon}
           <span>{overlayButtonLabel}</span>
         </button>
-        <button
-          className="ghost-button"
-          onClick={handleDemoScan}
-          disabled={isDemoDisabled}
-          title={demoButtonTitle}
-        >
-          {demoIcon}
-          {demoButtonLabel}
-        </button>
       </div>
     </header>
   );

src/features/layout/navigation.ts

@@ -1,4 +1,4 @@
-import { Layers3, Radar, Wand2, Eye } from "lucide-react";
+import { Layers3, Radar, Wand2, Eye, Wrench } from "lucide-react";
 import type { AppNavigationItem } from "./types";
 
 export const appNavigationItems: AppNavigationItem[] = [
@@ -6,5 +6,6 @@ export const appNavigationItems: AppNavigationItem[] = [
   { id: "triage", label: "Triage", icon: Layers3 },
   { id: "builds", label: "Builds", icon: Wand2 },
   { id: "overlay", label: "Overlay", icon: Eye },
+  { id: "diagnose", label: "Diagnose", icon: Wrench },
 ];
 

src/features/layout/types.ts

@@ -1,7 +1,7 @@
 import { type ComponentType, type ReactNode } from "react";
 import type { LucideProps } from "lucide-react";
 
-export type NavigationId = "scan" | "triage" | "builds" | "overlay";
+export type NavigationId = "scan" | "triage" | "builds" | "overlay" | "diagnose";
 
 export interface AppNavigationItem {
   id: NavigationId;